Neuro & Spine, the reference

Blood entering the skull has to overcome whatever pressure opposes its exit. Usually that back-pressure is intracranial pressure. If central venous pressure rises above it, for example when raised intrathoracic pressure from PEEP slows cranial venous drainage, venous pressure becomes the real outflow pressure the arterial side works against. Where injury has abolished autoregulation, flow follows perfusion pressure passively. Subtracting the smaller of the two pressures therefore overstates the perfusion the brain is actually getting, just where it matters most.

Wrong pressure subtracted in perfusion formula. This is what you get by subtracting intracranial pressure from mean arterial pressure, the version of the formula most people memorise. It is wrong here because central venous pressure is higher than intracranial pressure, so venous pressure is the real back-pressure. Subtracting the smaller value overestimates perfusion.

Both sources define perfusion pressure as mean arterial pressure minus the greater of intracranial and central venous pressure. One adds that PEEP can impair venous drainage from the cranium, and that injured regions lose autoregulation, so flow there depends passively on perfusion pressure.

Sources: FaustMayo review

Injured brain loses autoregulation, so blood flow tracks perfusion pressure passively; low pressure means ischaemia. Older reviews accepted a floor of 50; current Brain Trauma Foundation guidance narrowed the goal to 60-70, so 'above 50' remains correct but 60-70 is today's target. Driving it beyond 70 with fluids and pressors risks lung injury. When CPP is already high, the aim is to bring it into range, not accept it. A moderately obtunded patient who can be intubated conventionally needs neither awake intubation nor a surgical airway.

Targeting excessively high perfusion pressure. It is the number you get by subtracting ICP from the measured mean pressure, so it feels like the answer. But that is the patient's current perfusion pressure, well above target; tolerating or forcing values above the upper limit risks lung injury, and higher values worsen outcome.

Brain Trauma Foundation guidance sets the target for survival and good outcome at 60-70 mmHg and advises against aggressively forcing it above 70 because of respiratory failure; an older review gave 50-70; CPP is MAP minus ICP or CVP, whichever is greater.

Sources: Outside our books: Guidelines for the Management of Severe TBI, Fourth Edition (2017)FaustMayo review

Raised ICP reduces cerebral blood flow and risks ischaemia, as shown in 1948. Harm depends on duration as well as height: the share of hourly readings over 20 mmHg independently predicted outcome. The two books agree. Barash gives 20–25 mmHg for prolonged elevation. Brain Trauma Foundation data found 20 mmHg best matched 6-month outcome. Miller follows that guideline, treating at 22. In both, danger starts just above 20.

Borderline pressure mistaken for critical threshold. 15–20 looks raised because it sits just above the upper limit of normal, 15. But outcome data only turn clearly poor once pressure stays above 20. The 15–20 band is borderline, not the range tied to the worst outcome.

Barash gives normal ICP as 7–15 mmHg and links prolonged pressures above 20–25 mmHg with poor neurological outcome. Miller says pressures above 22 mmHg increase mortality and need treatment. Trauma data found 20 mmHg best predicted 6-month outcome.

Sources: Barash 9eMiller 10eOutside our books: Guidelines for the Management of Severe TBI, Fourth Edition (2017)

After trauma, raised ICP marks secondary brain injury and predicts death and poor outcome. An abnormal scan shows mass effect that is likely to raise pressure: haematoma, contusion, swelling, herniation or compressed basal cisterns. That is why the scan decides who gets a monitor. A normal scan carries low risk unless older age, posturing or hypotension add to it. Miller notes that these triggers rest on expert opinion, and the only randomised trial found no long-term outcome benefit. So the guideline indication remains standard practice, but its benefit is unproven.

Sedation alone justifies invasive monitoring. Direct pressure monitoring seems the obvious substitute when a sedated patient cannot be examined, but the guideline trigger differs: severe injury plus scan evidence of mass effect. Inability to examine does not qualify alone, nor does a normal scan without added risk features.

Trauma guidelines advise monitoring in severe TBI with an abnormal CT, meaning haematoma, contusion, swelling, herniation or compressed cisterns. With a normal CT, monitor only if two or more of these are present: age over 40, posturing, or systolic pressure below 90.

Sources: Miller 10eOutside our books: Guidelines for the Management of Severe TBI, Fourth Edition (2017)

Brain bulk is tissue, blood and CSF inside a fixed space. Carbon dioxide is the strongest physiological driver of cerebral blood flow, so correcting a high PaCO2 by ventilation quickly reduces brain blood content. Keep hypocapnia moderate, not below 23–25 mm Hg. Mannitol draws water out of brain across an osmotic gradient; furosemide speeds loss of intravascular water, helping sustain that gradient. Head elevation improves venous outflow. An anticonvulsant lowers neither blood volume nor brain water, so it gives no acute relaxation.

Dismissing diuretic as ineffective agent. Furosemide looks like a plain systemic diuretic with no brain-specific action, so people call it least useful. Given alongside mannitol, it hastens intravascular water loss and helps keep the osmotic gradient that shrinks brain. Phenytoin has no brain-shrinking action at all.

Textbooks list mild hyperventilation, osmotic diuretics, CSF drainage and positioning for venous drainage as ways to relax the brain. PaCO2 is the most potent physiological determinant of cerebral blood flow. Furosemide is sometimes paired with mannitol to maintain the osmotic gradient.

Sources: Stoelting 8eFaustMiller 10e

A cough or bucking on the tube abruptly raises intrathoracic pressure, transmitted at once to cerebral veins and arteries. Venous drainage is obstructed while arterial inflow continues to distend the vessels, so intracranial pressure rises abruptly, risking cerebral swelling and haemorrhage. Hypercapnia acts more slowly: cerebral blood flow rises by roughly 1 to 2 mL/100 g/min per mmHg rise in PaCO2, so mild hypercapnia causes a stepwise, proportionate increase. Low PEEP has very little effect on intrathoracic pressure.

Carbon dioxide effect overestimated in coughing. It is tempting because PaCO2 is the strongest everyday regulator of cerebral blood flow, and hypercapnia does dilate cerebral vessels. But this is mild hypercapnia, and it raises flow gradually. A cough loads both arterial and venous pressure at once, which is why paralysis is routinely used to prevent it.

Miller describes cough-driven intrathoracic pressure surges reaching both cerebral arteries and veins, with oedema, bleeding and raised ICP as consequences, and routine paralysis to prevent coughing. Barash finds low PEEP well tolerated. Cerebral blood flow changes by 1 to 2 mL/100 g/min per mmHg PaCO2.

Sources: Miller 10eBarash 9e

Lifting the head above heart level helps venous blood drain out of the skull. This lowers intracranial blood volume, so pressure falls. Keep the neck straight, because flexing or turning it compresses the jugular veins and blocks that drainage. Head-down tilt does the opposite: it congests the cerebral veins, triggers reflex vasodilation and increases intracranial blood volume. Sedation with analgesia and bolus mannitol or hypertonic saline are first-line measures for every patient, alongside head elevation. They are core treatment, not optional extras.

Reversal of head positioning effect. Hyperventilation is tempting because guidance now warns against aggressive hypocapnia, which can cause cerebral ischaemia. It still lowers ICP, and does so quickly, by constricting cerebral vessels. It is kept for brief rescue use. Head-down positioning is the manoeuvre that actually raises ICP.

Raising the head above the heart improves cerebral venous outflow and can lower ICP. Head-down positioning can raise it by increasing intracranial blood volume. Core measures for every head-injured patient include head elevation, mannitol or hypertonic saline boluses, and sedation with analgesia.

Sources: Stoelting 8eBarash 9eMiller 10e

Low PaCO2 constricts cerebral vessels, quickly shrinking blood volume and ICP, but this also reduces flow and risks ischaemia, most of all in the first 24 hours. The brain adapts to a sustained PaCO2, so an abrupt step from that baseline acts like a fresh large change. Guidance evolved: the Brain Trauma Foundation's current edition kept only a ban on prolonged prophylactic PaCO2 of 25 or less, merely restating its older temporising and avoid-early advice; Barash and Miller still allow brief rescue, so short targeted use satisfies both.

Premature hyperventilation before other measures. It sounds like disciplined, time-limited rescue, and it gives the surgeon what he asked for. But PaCO2 is already near target, and deeper hypocapnia cuts cerebral flow further. First-line measures such as osmotic therapy have not yet been tried.

Brain Trauma Foundation's newer edition only bans prolonged prophylactic PaCO2 of 25 or less, restating older advice. Barash avoids prolonged or prophylactic use, especially in the first 24 hours. Miller targets PaCO2 30–35, going to 30 only when sedation, drainage, paralysis and osmotics fail.

Sources: Miller 10eBarash 9e

Hypocapnia shrinks cerebral blood volume and ICP only while the CSF stays alkaline. The brain then actively lowers bicarbonate in the CSF and extracellular fluid. CSF pH drifts back to normal and blood flow follows, so the benefit fades even though arterial hypocapnia continues. The books give different timings but do not contradict each other. Barash and Stoelting say about 6 h, Faust 6–8 h and Miller 8–12 h. Where one figure is wanted, 6 h is the value most texts share.

Underestimating duration of hypocapnic effect. Ninety minutes is tempting because hypocapnic vasoconstriction starts almost at once, so the effect feels short-lived. But the effect ends through slow, active bicarbonate adjustment in the CSF. That takes hours, not minutes.

Barash and Stoelting say the ICP benefit of hypocapnia lasts about 6 h, because CSF pH returns to normal. Faust gives 6–8 h, through active bicarbonate change. Miller says CSF bicarbonate falls, so pH normalises over 8–12 h.

Sources: Barash 9eStoelting 8eMiller 10eFaust

An osmotic agent shrinks brain only if it stays in the plasma and pulls water out across a tight barrier. Where the barrier is damaged, Stoelting notes the agent leaks into brain tissue, drags water with it and can raise pressure paradoxically. Classic teaching pinned this on mannitol, which Miller says diffuses into leaky tissue causing rebound oedema; Miller's fluids chapter now adds that hypertonic saline's osmotic effect also falls with barrier disruption. So treat an intact barrier as a precondition for any osmotherapy; mannitol remains the textbook example.

Choosing less established osmotic therapy. Tempting because Miller says hypertonic saline's osmotic action also weakens when the barrier is disrupted, so it is defensible. It fails as the single best answer: Miller reports hypertonic saline working in patients no longer responding to mannitol, and the barrier requirement is classically taught for mannitol.

Stoelting: where the barrier is compromised, osmotic diuretics enter brain tissue and can paradoxically raise brain water and pressure. Miller: disruption reduces osmotic action of both mannitol and hypertonic saline; mannitol leaks into permeable tissue causing rebound oedema; hypertonic saline has anecdotally helped mannitol-refractory patients.

Sources: Miller 10eStoelting 8e

Tumours, abscesses and contusions damage the blood–brain barrier, so water leaks out of vessels into the extracellular space. Dexamethasone increases production of the tight-junction proteins that seal brain endothelial cells. This partly restores the barrier and cuts the leak. So it mainly stops new oedema forming and does little to clear oedema already present. Barrier permeability falls within 1 hour. Interstitial oedema, as in hydrocephalus, happens with the barrier intact, so there is no leak for the drug to close.

Steroids for wrong type of swelling. Steroids are thought of as broad anti-inflammatory, cell-protecting drugs, so cell swelling sounds like something they should treat. But dexamethasone works by tightening endothelial junctions, so it only helps oedema caused by a leaking barrier. The textbooks say it reduces vasogenic oedema only.

Dexamethasone reduces only vasogenic oedema, the barrier-leak type seen around tumours, abscesses and contusions. It does this by upregulating tight-junction proteins. It remains the main treatment for tumour oedema: it limits new oedema formation and lowers barrier permeability within 1 hour.

Sources: Barash 9eMiller 10e

The first impact is done. What worsens outcome is each later episode of low oxygen, low perfusion, fever or high glucose hitting vulnerable brain. Mayo's older review accepts a perfusion floor of 50 with MAP above 80. The current Brain Trauma Foundation guideline, like Barash's ICU table, raises it to 60–70, so aim there. For CO2, the guideline calls 35-45 normal ventilation. Barash's table says 35–40 and accepts slightly lower only after brief rescue hyperventilation. About 35 satisfies both.

Tight glucose targeting increases risk. Tight control sounds protective and looks like a precise target. The books set only an upper ceiling, and low glucose is itself a secondary insult to injured brain. Driving an in-range value down into a narrow band adds hypoglycaemia risk without benefit.

Mayo's review targets MAP above 80, CPP 50–70 and PaO2 above 60. Barash's ICU table lists CPP 60–70, SaO2 ≥95%, PaCO2 35–40, temperature ≤37°C, glucose below 180 and early enteral feeding. The trauma guideline sets CPP 60–70 and calls PaCO2 35-45 normal.

Sources: Mayo reviewBarash 9eOutside our books: Guidelines for the Management of Severe TBI, Fourth Edition (2017)

After brain injury, hypoxia and hypercapnia both cause secondary damage. Carbon dioxide directly affects intracranial pressure, which is why brief hyperventilation is used as a rescue when pressure rises. A deeply obtunded patient breathing spontaneously leaves carbon dioxide uncontrolled, and a rising PaCO2 shows this is already failing. Only a tube and controlled ventilation let you set arterial oxygen and carbon dioxide precisely. The ventilator settings then become part of the treatment.

Saturation substituted for coma depth. It looks like the smallest step that matches a mildly hypercapnic patient with good saturations. It fails because the book's threshold is based on coma depth, not oxygen saturation. At GCS 7 you need a tube and controlled ventilation to secure the airway and control carbon dioxide.

Miller advises intubation and ventilation at GCS 8 or less to prevent hypoxia and hypercapnia. When ICP is raised, it targets a PaO2 of 80–120 and a PaCO2 of 35–38 mm Hg. It notes that ventilator settings contribute to secondary brain damage.

Sources: Miller 10e

Plasma osmolality governs water movement into brain tissue. Any fluid that gives free water beyond ongoing losses lowers osmolality and swells both injured and healthy brain. Hypotonic and glucose-based solutions do this; normal saline does not, which is why it is the usual neurosurgical choice. A colloid gives no protective advantage. In traumatic brain injury, albumin was linked to more deaths than isotonic saline. So the goal is euvolaemia with an isotonic crystalloid, not oncotic support.

Colloid preference despite trial evidence. Albumin is tempting because a colloid seems to stay in the circulation, support blood pressure in a hypotensive, tachycardic patient and limit brain swelling. Trial evidence in traumatic brain injury showed more deaths with albumin than with isotonic saline, so it is avoided.

Textbooks advise isotonic, glucose-free crystalloids to keep patients euvolaemic. They warn that hypotonic fluids aggravate cerebral oedema because falling osmolarity swells brain. They name normal saline as the usual choice because it is isotonic, and they report higher traumatic brain injury mortality with albumin.

Sources: FaustStoelting 8eMiller 10e

Steroids were long given to damp post-traumatic inflammation without proof of benefit. The CRASH trial randomised head-injured patients to methylprednisolone or placebo; the steroid raised the relative risk of death by about 20% at 2 weeks, across every severity subgroup, and the severe-injury guideline data confirm more deaths with steroid than placebo. The evidence is an outcome signal, not a perfusion-pressure effect, so wherever falling CPP is blamed, the answer is still the steroid. Pooled data showed propofol, opioids and benzodiazepines lowered ICP and sedated without adding deaths.

Steroid mortality attributed to sedative. Propofol tempts because it lowers arterial pressure, and so CPP, and long infusions can cause a fatal infusion syndrome. Yet pooled analysis tied no sedative, propofol included, to extra deaths, and propofol helps lower ICP. Only the corticosteroid raised mortality.

A large randomised trial found methylprednisolone raised relative risk of death about 20% at 2 weeks across all severity groups. Guideline data show higher mortality with steroid than placebo, and a meta-analysis named corticosteroids the only mortality-raising common TBI drug. Guidance advises against steroids.

Sources: Barash 9eOutside our books: Guidelines for the Management of Severe TBI, Fourth Edition (2017)Miller 10e

Levodopa is a dopamine precursor with a short half-life, so a missed dose soon strips the striatum of dopamine: rigidity returns and abrupt withdrawal can provoke a hyperpyrexic crisis. Tablets therefore continue with a sip of water while fasting and are repeated through a tube in prolonged surgery. There is no safe intravenous levodopa; its dopamine metabolite causes arrhythmia and hypertension. Miller's, assuming oral-only drugs, relies on the nasogastric route; Barash and newer reviews add subcutaneous apomorphine as the bridge when the gut cannot be used.

Intravenous levodopa dosing attempted. It captures the right instinct, not letting levodopa lapse during a long operation, so it looks like the safe choice. It fails on route: levodopa is given only enterally, intravenous dosing risks arrhythmia and hypertension, and no source gives a fixed six-hour trigger.

Guidance advises taking usual drugs with a sip of water right up to induction and, given the short half-life and withdrawal risk, continuing enteral doses in long procedures. IV levodopa is discouraged for arrhythmia and hypertension; subcutaneous apomorphine covers delayed postoperative restart.

Sources: Outside our books: Parkinson's disease (2017)Outside our books: Preoperative Evaluation of Parkinson's Disease (2021)Outside our books: Parkinson's Disease (2026)

Diathermy current can damage the intracranial leads, heat the electrode tips, or suppress or reprogramme the generator, so the device goes off for any operation using diathermy, and bipolar is preferred. The switch-off concerns electrical interference, not the anaesthetic: without diathermy it may stay on. In advanced Parkinson's disease, switching off brings back rigidity and dystonia that can hinder mask ventilation and intubation, so it may stay on through induction and be switched off before diathermy starts. Restart it before or at emergence and check function.

Refer to the device team instead. Referring feels like the safe, cautious choice for an unfamiliar implanted device. But the anaesthetist already has a defined plan: stimulator off before diathermy, bipolar only, restart and check afterwards. The device team advises on settings; it does not decide the anaesthetic, and a referral does not replace that plan.

Diathermy is permitted but may injure the leads or suppress or reprogramme the generator, so the device is switched off immediately before induction and bipolar is used. It is off for the surgery, restarted in recovery, and checked afterwards for normal function.

Sources: Outside our books: Parkinson's disease (2017)Mayo review

Stoelting explains that warming may cause complete conduction block in demyelinated nerves, so even a small temperature rise can bring back or worsen deficits; Miller's also calls temperature monitoring critical. Barash takes a wider view: anaesthesia itself seldom alters the disease course, and infection, high fever and emotional stress are the likelier perioperative triggers. The views fit together: stress and infection contribute, but a rise in temperature is the one trigger every source names, the only one with a stated mechanism, and the one the anaesthetist can directly prevent.

Emotional stress over documented hyperthermia. Emotional stress is tempting because Barash lists it among the perioperative contributors to relapse. But only that source names it, and it sits alongside hyperpyrexia. A rise in temperature is named by every source, has a proposed mechanism, and is the factor all of them say to monitor and prevent.

Stoelting says a rise of even 1°C can precipitate an exacerbation, possibly by blocking conduction in demyelinated nerves. Miller's calls temperature monitoring critical. Barash finds that anaesthesia usually does not change the disease, and blames relapses on infection, hyperpyrexia and emotional stress.

Sources: Stoelting 8eMiller 10eBarash 9e

In Becker, dystrophin is reduced rather than absent, so muscle and heart fail more slowly than in Duchenne. Barash says death usually occurs in the fifth or sixth decade, shorter than normal; Stoelting adds that the mildest cases may live a normal span, and Miller notes a wide severity range. Life is therefore shortened on average, but not for every patient. Heart disease can be silent, so asymptomatic patients are screened regularly, and more often once symptoms appear. Female carriers can also have cardiac abnormalities.

Overstating universal presence of cardiomyopathy. Heart involvement is a real Becker concern and screening is advised, so a cardiac option feels safe. But screening is aimed at asymptomatic patients, and many have no detectable heart disease yet, so 'always' overstates it. The statement that holds is the shortened life expectancy for the group.

Becker comes from reduced dystrophin and follows a Duchenne-like but milder course. Death usually comes in the fifth or sixth decade, and severity varies widely. Asymptomatic patients need a cardiac review every 5 years, more often if symptoms appear. Female carriers may have cardiac disease.

Sources: Barash 9eMiller 10e

Rheumatoid disease loosens the joint between the atlas and the odontoid peg, so the atlas slides away from the dens. Once the peg is displaced, it can press on the upper cord or medulla, or block the vertebral arteries. Moving the neck during airway handling can push it further. A lateral film showing a gap of more than 3 mm between the anterior arch of the atlas and the dens confirms subluxation. Early aggressive therapy has made severe disease less common, but it still needs to be looked for.

Degenerative stenosis confused with rheumatoid. It is tempting because canal narrowing also threatens the cord, and older patients often have degenerative spondylosis. It is not the rheumatoid lesion, though. Rheumatoid arthritis targets the joint where the atlas meets the odontoid peg, and slippage at that joint is what endangers the brainstem during intubation.

Neck involvement is common in rheumatoid arthritis, and slippage between the atlas and the odontoid peg is its most important cervical abnormality. A displaced peg can compress the cord or medulla or block the vertebral arteries. On imaging, a gap above 3 mm confirms subluxation.

Sources: Stoelting 8eFaust

When a disc compresses one nerve root, it causes pain along one dermatome or weakness in a few muscles. When it presses on the cord itself, it disturbs motor, sensory and autonomic function at the level of the lesion and below it. The cervical cord carries the pathways to both arms, so disease there, such as myelopathy or a syrinx, weakens both upper limbs. CT or MRI of the neck shows the lesion and its level. Degenerative neck disease also changes preoperative airway planning.

Vascular imaging for cord compression. In a patient awaiting surgery, arm weakness can look like a transient ischaemic attack and push you toward a vascular work-up. But arm weakness that is bilateral, heavy and sometimes painful fits cord or root compression in the neck, and a carotid scan cannot show that lesion.

Cervical myelopathy and syringomyelia cause upper-limb weakness. Cord compression produces motor, sensory and autonomic features below the lesion, and CT or MRI confirms a herniated disc and its level. Degenerative cervical disease needs preoperative symptom review and a thorough airway assessment.

Sources: Stoelting 8eMiller 10eBarash 9e

Both types of attack are classic features of carotid atheroma. Plaque at the bifurcation sheds emboli into the same carotid territory, which supplies both the eye and the hemisphere, so the symptoms come and go. Carotid ultrasound is non-invasive, can be done at the bedside and measures how narrow the vessel is. That measurement decides treatment. A symptomatic patient with severe narrowing is referred for early endarterectomy. A cardiac source of emboli should still be looked for.

Invasive imaging before initial ultrasound. Angiography sounds like the definitive test for a vascular cause, so it is tempting. But it is invasive and it is not the first step. The source names carotid ultrasound as the test that grades the stenosis, and the grade is what decides management after a transient ischaemic attack.

Carotid disease is usually embolic, not occlusive, causing brief monocular blindness, weakness, clumsiness or speech disturbance. In transient attacks, ultrasound can measure stenosis. Over 70% stenosis risks infarction and lasting deficits.

Sources: Barash 9eStoelting 8eFaust

Spondylosis narrows the cervical canal, so the cord has little room. Extending the neck, as for thyroid or parathyroid surgery, can injure the cord and usually gives a central cord pattern. The damage lies in the cord and the soft tissue around it, such as disc, haematoma or stenosis. Plain films and CT show these poorly. MRI shows the cord and whatever is pressing on it, so it confirms the cause and shows whether decompression is needed.

Brain imaging for spinal cord lesion. Tetraparesis after anaesthesia suggests stroke, so a brain scan seems sensible. However, a sensory level at a cervical dermatome places the lesion in the cervical cord, not the brain. In a patient with neck disease whose neck was extended, image the cervical spine.

Central cord syndrome typically follows a hyperextension injury in people with cervical spondylosis. CT and plain films show the cord and nearby soft tissue less well than MRI. MRI shows ongoing cord compression and its cause, including disc herniation, haematoma and pre-existing canal stenosis.

Sources: Outside our books: International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019 (2021)Outside our books: A Clinical Practice Guideline for the Management of Acute Spinal Cord Injury: Introduction, Rationale, and Scope (2017)Barash 9e

Blood collecting in the vertebral canal squeezes the cord and roots and makes them ischaemic. The damage becomes permanent unless the clot is found and removed quickly, so the time to decompression decides recovery. A new postoperative deficit can also come from direct cord injury, graft complications or spinal misalignment, so an accurate image must come before any return to theatre. MRI has displaced CT and myelography since it is both sensitive and specific. Observing or monitoring only uses up the time in which rescue is possible.

Observation delays diagnosis of compression. Baseline recording and observation seems careful, and some haematomas settle without surgery when there is no paralysis. But this deficit is new compared with the preoperative examination. Each hour of observation risks permanent compression, and only imaging can distinguish haematoma from cord injury or graft problems.

Outside reviews advise suspecting epidural haematoma whenever a new deficit follows surgery. They note that rapid reoperation decides full recovery and insist on radiological diagnosis first. MRI, being sensitive and specific, has replaced CT and myelography as the screening test.

Sources: Outside our books: Postoperative Spinal Epidural Hematoma: Risk Factor and Clinical Outcome (2009)Outside our books: Spinal Epidural Hematoma (2026)Miller 10e

Antibodies leave the endplate with fewer working acetylcholine receptors. A small amount of non-depolariser therefore blocks enough of them to cause weakness. Succinylcholine has fewer receptors to depolarise, so its effective dose rises about 2.6-fold. Barash gives the older stance: avoid blockers, let a volatile agent provide relaxation for intubation and surgery, and cut doses to one-half to two-thirds when a blocker is unavoidable. Miller calls avoidance the traditional advice and says sugammadex now makes careful use of steroidal blockers acceptable.

Absolute prohibition on neuromuscular agents. This echoes Barash and the traditional teaching, and volatile-only relaxation is indeed first choice when no blocker is needed. As an absolute rule it fails: when surgery needs relaxation, Miller accepts cautious, reduced steroidal dosing because sugammadex can reverse it.

Myasthenic patients are highly sensitive to non-depolarisers yet resistant to succinylcholine, whose ED95 is 2.6 times normal. Barash favours volatile relaxation and, if needed, one-half to two-thirds doses. Miller says sugammadex has moved practice from traditional avoidance toward judicious use of steroidal blockers.

Sources: Miller 10eFaustBarash 9e

Circulating antibodies target the alpha subunit of the muscle-type nicotinic receptor on the endplate and spare neural-type receptors. They block acetylcholine binding and cross-link receptors, which the cell then takes in and breaks down. With fewer working receptors, a single effort may succeed, but repeated or sustained contraction fails, so weakness builds with activity. Ocular, bulbar, limb and respiratory muscles can all be involved, not only cranial ones. The endplate already has too few spare receptors, so induction alone often gives enough relaxation for intubation.

Congenital inheritance instead of acquired. It is tempting because most of it is right: antibodies do destroy postsynaptic receptors, and babies of affected mothers can be weak at birth. But the disease is acquired, not inherited. The newborn weakness is short-lived and comes from maternal antibody crossing the placenta, not from a gene.

Antibodies against the alpha subunit of postsynaptic muscle-type nicotinic receptors block and cross-link them, causing their breakdown. Ocular, bulbar, limb and respiratory muscle weakness and fatigability worsen with activity. Intubation is often possible without relaxants.

Sources: Miller 10eFaustStoelting 8e

When a muscle loses its nerve supply, receptors are no longer kept at the junction. The muscle then makes immature nicotinic receptors across its whole membrane. These receptors stay open longer and are very sensitive to depolarising drugs, so suxamethonium can release enough potassium to cause dangerous hyperkalaemia. The opposite happens with constant agonist exposure. When cholinesterase is blocked, acetylcholine builds up and stimulates the receptors non-stop, so mature receptors are lost. Myasthenia is also classed as a state of reduced receptor numbers.

Upregulation mistaken in myasthenia. It is the best-known disease of acetylcholine receptors, and it changes how patients respond to relaxants, so it feels like the right answer. But myasthenia lowers the number of functional receptors. The textbooks list it as down-regulation, alongside cholinesterase inhibition.

Textbooks list spinal cord injury, Guillain–Barré, burns, stroke and prolonged immobility as causes of up-regulation, with immature receptors spreading beyond the junction. They list myasthenia, anticholinesterase poisoning and organophosphate poisoning as causes of down-regulation, which follows from continual agonist stimulation.

Sources: Barash 9eMiller 10e

Suxamethonium depolarises the muscle membrane and first produces fasciculations. In myotonic muscle, that stimulus makes the myotonia worse. Instead of brief twitching followed by flaccid paralysis, the patient may develop spasm or a full myotonic crisis. Rigid jaw and chest wall muscles can then make mask ventilation and laryngoscopy difficult. This contracture is not malignant hyperthermia. These patients are also more sensitive to opioids, benzodiazepines and non-depolarisers, so a short-acting blocker is the safer choice.

Resistance to blockers in myotonia. This is tempting because disorders with upregulated acetylcholine receptors do make patients resist non-depolarisers. Myotonic dystrophy is not one of them. Here non-depolarisers are reported to cause prolonged or enhanced weakness, so these patients are sensitive to them. The typical effect of suxamethonium in this disease is contracture.

The sources advise avoiding suxamethonium because of an exaggerated contracture that may hinder ventilation and intubation. Its fasciculations can worsen myotonia or cause spasm. Non-depolarisers are reported to cause prolonged weakness, and a short-acting blocker is preferred when relaxation is required.

Sources: Barash 9eFaust

The source puts the resistance down to chronic anticonvulsant treatment, which many patients with cerebral palsy receive. It groups these patients with epilepsy, not with denervation states. Upregulation of acetylcholine receptors is a different process. It explains exaggerated potassium release after suxamethonium in motor neuron lesions, burns, disuse atrophy, trauma and prolonged intensive-care paralysis. So in a medicated patient with cerebral palsy, the expected problem is that non-depolarising agents work less well than usual.

Exaggerated suxamethonium response in CP. It is tempting because cerebral palsy sounds like a motor neuron lesion, and upregulated receptors cause exaggerated responses to suxamethonium. But the source lists cerebral palsy among anticonvulsant-treated conditions. For those conditions it describes resistance to non-depolarisers, not an abnormal suxamethonium response.

Faust says that conditions treated with long-term anticonvulsants, naming cerebral palsy and epilepsy, show resistance to neuromuscular blockers. Separately, it links receptor upregulation to lethal potassium release after suxamethonium in motor neuron lesions, burns, disuse atrophy, severe trauma and infection.

Sources: Faust

Barash warns that the hyperkalaemia danger of suxamethonium persists after recovery from GBS, so it stays off the list. For neuraxial block the books differ in tone, not verdict: Barash reports it in routine use in theatre and labour; the more recent Miller edition calls regional techniques controversial because they have been implicated in neurological worsening, yet does not forbid them. So a spinal is the pick, after recording the existing deficit, while a blanket 'regional is safe' is exactly what Miller disputes. Immunotherapy helps only early in active disease.

Immunotherapy outside therapeutic window. Recent ventilation and residual weakness make treating the disease feel protective. But immunotherapy works only when started within two weeks of symptom onset; six months on there is no active illness to treat, and no source supports giving it to shield a patient at surgery.

Barash reports neuraxial block remains in common use for GBS in theatre and labour, and warns suxamethonium's hyperkalaemia risk can outlast recovery; Miller finds general anaesthesia well tolerated but regional controversial after reports of worsening; immunotherapy works best begun within two weeks.

Sources: Barash 9eMiller 10e

Weak respiratory and pharyngeal muscles and heightened sensitivity to induction agents make general anaesthesia riskier, so opioid-sparing regional techniques are favoured. Miller reports neuraxial block as the commonly used option and warns that peripheral blocks are difficult. Faust accepts either, provided ultrasound replaces the nerve stimulator, as electrical stimulation can provoke myotonia. Safe under both: spinal or lumbar epidural. Peripheral block is acceptable only with ultrasound and full coverage of the field. If general anaesthesia is needed, rapid sequence intubation secures the weak airway; a laryngeal mask does not.

Single peripheral block incomplete coverage. A sciatic block looks ideal: it is regional and avoids both neuraxial and general anaesthesia. But the skin over the medial malleolus and medial ankle is saphenous territory, so a sciatic block alone leaves the incision unblocked. Peripheral blocks are also flagged as difficult in these patients.

Miller: neuraxial block is often used in myotonic dystrophy to spare opioids; peripheral blocks can be difficult. Faust: neuraxial or regional techniques help if ultrasound-guided, as nerve stimulation may trigger myotonic crisis; rapid sequence intubation is preferred. Saphenous nerve supplies the medial ankle.

Sources: Miller 10eFaust

Denervated muscle in ALS has extra acetylcholine receptors, so suxamethonium can release enough potassium to cause a lethal rise. Bulbar weakness brings aspiration risk and ventilatory reserve is poor. These patients are also unusually sensitive to opioids and sedatives, so any opioid, including intrathecal morphine, risks hypoventilation and prolonged ventilation. A spinal with local anaesthetic alone avoids airway handling, relaxants and respiratory depressants. Barash accepts general anaesthesia with a reduced non-depolarising dose and fully confirmed reversal, but only as the fallback when regional is not possible.

Neuromuscular agent when neuraxial available. Reduced-dose rocuronium may be used in ALS, provided reversal is proven, but only as a fallback when regional anaesthesia is not possible. Here a spinal is available and avoids airway instrumentation altogether. The reduced dose is also far below the standard rapid-sequence dose.

ALS patients are highly sensitive to sedatives, opioids and anaesthetics, and risk aspiration and respiratory failure. Regional anaesthesia, short-acting drugs and opioid avoidance reduce prolonged intubation. Avoid suxamethonium (hyperkalaemia). Use non-depolarisers only at reduced doses with proven reversal.

Sources: Miller 10eBarash 9e

Ester local anaesthetics are broken down in plasma by cholinesterase. Amides are cleared by enzymes in the liver. Anticholinesterase drugs such as pyridostigmine are the mainstay of myasthenia treatment, and they also suppress plasma cholinesterase. An ester can therefore act for longer and stay in the body longer than expected. Amide clearance is not affected by these drugs. Neuraxial block is not the problem in itself: it is acceptable as long as breathing and muscle strength are watched closely.

Ester metabolism impaired by anticholinesterase. Esters such as chloroprocaine are normally hydrolysed very quickly in plasma, so they look like the short-acting, low-toxicity choice. That speed depends on plasma cholinesterase. The patient's anticholinesterase therapy suppresses this enzyme, so the ester's duration becomes prolonged and unpredictable.

Neuraxial blocks are considered safe in myasthenia if ventilation and muscle function can be monitored. Ester agents are hydrolysed by plasma cholinesterase, which anticholinesterase therapy inhibits, so their action may be prolonged. Amides are metabolised in the liver instead.

Sources: FaustMiller 10e

When the head is above the heart, a column of blood sits between them, so pressure measured at the brain's base is lower than at the heart or arm. Cerebral perfusion depends on the pressure reaching the circle of Willis, and the ear canal is a surface marker for it. A transducer levelled at the heart therefore overstates the pressure reaching the brain. In the sitting posture, the gap between brachial and brain mean pressure is about 25 mm Hg.

Heart-level zeroing overestimates cerebral pressure. Zeroing at heart level is routine for supine patients, so it feels like the safe default. With the head raised, it shows the pressure at the heart, not the brain. It overestimates cerebral perfusion and can hide dangerous cerebral hypotension.

The textbooks agree that levelling the transducer at the external auditory meatus, which approximates the circle of Willis, is the gold standard for cerebral perfusion pressure in sitting patients. In that posture the arm-to-brain mean pressure gradient is about 25 mm Hg.

Sources: Stoelting 8eFaustMiller 10e

The EVD reads ventricular pressure, so the transducer's zero must sit in the horizontal plane of the foramen of Monro, a midline structure deep in the head. Supine, the ear canal lies roughly at that height, which is the textbook landmark. Turn the patient on their side and the ears become top and bottom of the head; the facial midline now shares the foramen's height, so journal sources, not textbooks, use the glabella. External landmarks are only approximations, and mislevelling causes over- or underdrainage.

Ear landmark inaccurate in lateral position. The ear canal is the landmark every textbook teaches, so it feels safe. But that holds only supine; in the lateral position the ears sit above and below the midline, so zeroing there misplaces the reference well away from the foramen.

Anaesthesia textbooks zero the EVD transducer at the external auditory meatus; a review says the tragus approximates the foramen of Monro. A neurosurgical study lists the glabella or nose tip as lateral-position references and says the transducer must be re-levelled whenever the head moves.

Sources: Barash 9eOutside our books: Anatomical Approaches for Insertion Sites of External Ventricular Drainage Catheters (2026)Outside our books: Best zero level for external ICP transducer (2019)

When the head is forced down onto the chest, the cervical canal lengthens. This stretches the spinal cord and the small vessels that supply it. Blood flow to the midcervical segment falls, and the cord becomes ischaemic, sometimes to the point of infarction. Direct mechanical compression of the cord adds to the damage. The result is paralysis below roughly the fifth cervical level. Limiting flexion keeps a gap between the chin and the sternal notch, which protects cord perfusion.

Eye pressure confused with cord ischaemia. It tempts because it is a well-known positioning injury that also causes permanent disability. However, it comes from external pressure on the eye, not from neck flexion. The injury the sources link to flexion in the seated patient is cervical cord ischaemia, which causes quadriplegia.

Hyperflexion stretches the cord and compromises its midcervical blood supply; compression is a second proposed mechanism. The result is paralysis below about the fifth cervical level. To prevent it, keep at least two fingerbreadths between chin and sternal notch.

Sources: Barash 9eFaust

Ischaemic optic neuropathy after prone spine surgery is thought to come from venous congestion in the optic canal. Two things raise that venous pressure and so lower the pressure perfusing the optic nerve: raised abdominal pressure in an obese prone patient, and many hours face-down. Keeping the head up lets venous blood drain. Staging long or bloody operations shortens the exposure. Deliberate hypotension would cut perfusion further, so it is not routine in high-risk patients and is judged patient by patient.

Hypotension impairs optic nerve perfusion. Deliberate hypotension reduces bleeding in scoliosis surgery, and heavy blood loss is itself a reason to stage the operation. However, lowering arterial pressure while the optic canal is congested further reduces optic nerve perfusion. Experts are uneasy and leave it to individual judgement in high-risk patients.

Guidance advises positioning high-risk patients with the head at or higher than heart height, avoiding direct eye pressure, and staging operations expected to be long or bloody. Obesity-related abdominal pressure and long anaesthetics raise optic canal venous congestion. Deliberate hypotension is decided case by case.

Sources: Miller 10eBarash 9eOutside our books: Practice Advisory for Perioperative Visual Loss Associated with Spine Surgery 2019: An Updated Report by the American Society of Anesthesiologists Task Force on Perioperative Visual Loss, the North American Neuro-Ophthalmology Society, and the Society for Neuroscience in Anesthesiology and Critical Care (2019)

Wernicke's area lies in the posterior superior temporal cortex of the dominant hemisphere. It acts as the language association cortex, where heard language is decoded and understood. If it is damaged, the patient loses comprehension, which is receptive aphasia. Broca's area in the frontal lobe handles producing speech, so damage there causes expressive aphasia. The motor strip controls movement. Keeping the patient awake with local anaesthesia and sedation lets the team check language as they go, so they can stop before the function at risk is lost.

Speech testing near receptive language area. It is tempting because Broca's and Wernicke's areas are both language areas, and speaking is the part of language you can see. But an expressive deficit comes from Broca's frontal cortex. Near Wernicke's area the function at risk is understanding, so the test must check comprehension.

The texts link Wernicke's area to understanding language and Broca's area to producing speech. Damage to Wernicke's area causes receptive aphasia and damage to Broca's causes expressive aphasia. Temporal-lobe resections near language cortex can be done awake so language can be tested during surgery.

Sources: FaustBarash 9e

Textbooks list the complications of awake craniotomy but do not rank them. The list includes nausea, vomiting, respiratory problems and a tight brain, which are usually mild and under 10% in experienced centres. Bleeding and loss of consciousness are not on that list. Studies outside the textbooks disagree depending on what they count. A cohort that recorded every complication found hypertension the commonest. A meta-analysis that looked only at seizures found them in 8.4%, with higher risk after previous seizures, on antiepileptic drugs or with frontal lesions.

Consciousness loss as frequent complication. Loss of consciousness sounds likely because heavy sedation, airway trouble and seizures all happen during awake craniotomy. But the textbook lists name respiratory problems and a tight brain, not loss of consciousness, and no study here reports it as a common intraoperative event.

A major textbook lists nausea, vomiting, respiratory problems and tight brain as usually mild and under 10%. Outside the textbooks, one cohort found hypertension the commonest. A seizure meta-analysis found seizures in 8.4%, more often with previous seizures, antiepileptic drugs or frontal lesions.

Sources: Miller 10eOutside our books: Awake Craniotomy Anesthesia: A Comparison of the Monitored Anesthesia Care and Asleep-Awake-Asleep Techniques (2017)Outside our books: Risk factors and predictors of intraoperative seizures during awake craniotomy: A systematic review and meta-analysis (2023)

Coughing and blood-pressure surges risk surgical bleeding and raised intracranial pressure. Opioids blunt the cough reflex, so Miller's authors give as much as still allows spontaneous breathing, withdraw inhaled agents and top up with small propofol doses or a low infusion for a calm, rapid wake-up. Barash reaches the same goal with a low-dose remifentanil infusion and/or intravenous or tracheal lidocaine. Miller also names lidocaine with labetalol or esmolol as the usual reactive treatment for late hypertension, so the approaches combine rather than compete.

Excessive lidocaine dose for emergence. Lidocaine is tempting because Miller describes lidocaine plus vasoactive drugs as the usual management of late craniotomy hypertension. However, the stated dose is incorrect, far above Miller's modest bolus before dressing application, and that passage concerns treating hypertension, not planned smooth emergence.

Barash advises avoiding cough in every craniotomy, suggesting low-dose remifentanil and/or intravenous or tracheal lidocaine. Miller's authors favour maximal opioid compatible with spontaneous breathing, withdraw inhaled agents and supplement with propofol boluses or low-dose infusion; lidocaine with labetalol or esmolol treats emergence hypertension.

Sources: Miller 10eBarash 9e

Pain after craniotomy is significant but often undertreated, because clinicians worry that opioids will cause hypoventilation and raise intracranial pressure. Leaving the pain untreated is also harmful, so aim for good analgesia that still allows repeated neurological checks. Short-acting opioids can be titrated to effect and wear off quickly, so any sedation cannot hide a falling conscious level for long. Local anaesthetic infiltration, intravenous paracetamol or dexmedetomidine reduce the opioid needed. Large or long-lasting sedating doses make the neurological examination unreliable.

Morphine obscures neurological assessment. Intramuscular morphine is the usual ward analgesic, and it does relieve pain. But it lasts a long time and cannot be titrated finely. The sedation and hypoventilation it can cause may cloud the neurological examination and raise intracranial pressure, which is exactly what analgesia after craniotomy must avoid.

Pain after craniotomy is significant but often underestimated, and opioids are held back for fear of hypoventilation raising ICP. Treatment should be multimodal: short-acting opioids such as fentanyl or remifentanil, local infiltration, intravenous paracetamol or dexmedetomidine, avoiding sedating doses.

Sources: Barash 9eMiller 10e

Recent food means gastric contents must be presumed, so induction and intubation follow a rapid sequence to shorten the time the airway is unprotected. A blocked shunt leaves the brain with little room, so any transient rise in intracranial pressure matters; succinylcholine can cause one, and paediatric practice has moved away from it for routine intubation. A Cochrane review found high-dose rocuronium, dosed per kilogram, gave intubating conditions comparable to succinylcholine. It therefore gives rapid-sequence speed without the depolarising drug's pressure rise.

Succinylcholine standard dose raises intracranial pressure. It is the classic rapid-sequence relaxant, and this dose matches the standard per-kilogram paediatric dose for her weight, so the dose is not the flaw. It fails because it is no longer routine for children's airways, risks hyperkalaemia from undiagnosed myopathy, and can raise intracranial pressure.

Presumed gastric contents call for rapid sequence induction. A Cochrane review found rocuronium 1.2 mg/kg gave intubating conditions no different from succinylcholine. Succinylcholine is no longer routine for children's airways and may increase intracranial pressure.

Sources: Barash 9eMiller 10eStoelting 8e

Raising the head above the heart drains venous blood from the nose and sella, which reduces ooze. The main textbook supports a head-up posture. A tumour reaching the cavernous sinus can bleed heavily, so blood is grouped and screened in advance. Controlled hypotension comes from outside the textbooks. An Endotext review makes it the goal while keeping normocapnia and cerebral perfusion. An otorhinolaryngology review keeps mean arterial pressure above 60 mmHg to protect cerebral flow. In chronic hypertension autoregulation is reset upward, so any lowering stays mild.

Hyperventilation tempts but does not stop bleeding. Hyperventilation is tempting because it shrinks the brain, but it does nothing for bleeding from the mucosa or venous sinuses. Surgeons sometimes ask for hypocapnia to stop the arachnoid bulging into the sella. The anaesthetic baseline is still normocapnia, and suprasellar tumours need normal carbon dioxide to descend.

From outside the textbooks: one review sets controlled hypotension with preserved cerebral perfusion and normocapnia as the goal; another finds mean arterial pressure above 60 mmHg keeps middle cerebral flow above 50% of baseline. The textbook advises head-up posture; group and screen suits cavernous extension.

Sources: Outside our books: Pituitary Surgery (2026)Outside our books: Perioperative management of endoscopic transsphenoidal pituitary surgery (2020)Miller 10e

Handling the carotid bifurcation stimulates glossopharyngeal afferents, which sets off a reflex change in heart rate and blood pressure. Infiltrating local anaesthetic at the bifurcation blocks that afferent limb. In these patients cerebral autoregulation may be shifted, so a swing in pressure can reduce brain perfusion. For that reason pressure is held within 20% of the patient's own baseline. Awake regional and general anaesthesia give similar neurological outcomes. The regional technique has the advantage that the surgical team can keep checking the patient's neurology directly.

Cushing reflex misleads glossopharyngeal reflex source. It sounds right as a well-known reflex altering heart rate and blood pressure, but the Cushing reflex is triggered by raised intracranial pressure. The relevant reflex here arises from surgical stimulation at the carotid bifurcation via the glossopharyngeal nerve, and local infiltration blocks it.

When surgeons work at the carotid bifurcation, glossopharyngeal stimulation can cause reflex haemodynamic changes, which local infiltration there can block. Blood pressure should stay within 20% of baseline because autoregulation may be shifted. Awake and asleep techniques give similar neurological outcomes.

Sources: Barash 9e

Once the carotid is clamped, the hemisphere on that side depends on collateral inflow from the opposite side. That inflow is driven by systemic pressure. Miller advises keeping pressure high-normal throughout, and especially while clamped. Where no neurophysiological monitoring is used, it suggests going 10% to 20% above baseline. The limit is the heart. Raising pressure and heart rate with vasopressors can provoke myocardial ischaemia. So aim for the target and don't overshoot it.

Normal pressure inadequate for collateral flow. A pressure of 100/60 with a heart rate of 60 looks stable, so doing nothing feels safe. But this is not high-normal. Once the clamp goes on, collateral flow at this pressure may be too low for the brain. Deepening anaesthesia or giving nitroglycerin would lower it further.

Keep arterial pressure high-normal, especially while the carotid is clamped, to boost collateral flow. Without neurophysiological monitoring, aim 10% to 20% above baseline. Get there with light general anaesthesia or sympathomimetics such as phenylephrine. Vasopressor-driven rises in pressure and heart rate risk myocardial ischaemia.

Sources: Miller 10e

Transcranial Doppler insonates the middle cerebral artery, the territory endangered when the carotid is clamped; its maximum velocity tracks cerebral blood flow, so a fall after cross-clamping signals hypoperfusion, and it counts microemboli that global monitors such as EEG can miss. Barash and Stoelting value it for this; Miller explains why it never became routine: no usable signal in up to 20% of patients. Stoelting still ranks awake neurological assessment as most reliable, so Doppler suits the anaesthetised patient.

ECG tempts cardiac not cerebral monitoring. ECG is tempting because haemodynamic monitoring sounds cardiovascular, and these vascular patients do carry cardiac risk. But the question is about the brain: after clamping, the danger is hemispheric hypoperfusion and emboli, which only a cerebral flow monitor such as transcranial Doppler reveals.

TCD follows middle cerebral artery velocity as a stand-in for cerebral flow and detects microemboli that global monitors miss, having predicted deficits despite a normal EEG; it fails to give a usable signal in up to 20% of patients, and awake assessment is most reliable.

Sources: Barash 9eMiller 10eStoelting 8e

The seizure surges blood pressure and cerebral blood flow beyond autoregulation, sharply raising intracranial pressure. A brain with a mass or injury cannot tolerate this, and aneurysm walls take extra stress. Stoelting therefore forbids ECT with a space-occupying lesion or head injury and names aneurysm as a contraindication. Faust also lists mass as absolute, together with recent infarction and recent stroke. Eye pressure always rises during the seizure, yet Faust lists glaucoma, retinal detachment and severe osteoporosis only as relative.

Detached retina relative not absolute contraindication. The seizure always raises intraocular pressure, so a detached retina feels like a hard stop. The books list it only as a relative contraindication, a risk to weigh against the benefit. What they prohibit is a sharp rise in intracranial pressure over a mass.

Faust lists intracranial mass, recent myocardial infarction and recent stroke as absolute contraindications, and glaucoma, retinal detachment and severe osteoporosis as relative. Stoelting notes seizure-driven pressure surges can raise intracranial pressure, so ECT is prohibited with space-occupying lesions, head injury or aneurysm.

Sources: FaustStoelting 8e

The treatment effect depends on an adequate seizure. At least 25 seconds is recommended for antidepressant benefit. Most hypnotics are anticonvulsant, and the effect grows with dose. Volatile agents, and barbiturates or propofol at anaesthetic doses, markedly suppress epileptiform activity. Deeper or longer anaesthesia therefore shortens the seizure and weakens treatment. The aim is only a brief loss of awareness covering the paralysis and shock, followed by rapid waking.

Deep anaesthesia wrongly suppresses seizure therapy. This option is clumsily worded, so it reads like a false claim. Its intended meaning is true: suppressing the seizure reduces how well ECT works. The statement that plainly contradicts the books is the one calling for prolonged, deep anaesthesia.

Anaesthesia for ECT should be short, allow the seizure's physiological effects to be controlled, and interfere as little as possible with seizure activity or duration; a small hypnotic dose aiming for quick waking is usual, and a seizure of at least 25 seconds is recommended.

Sources: Stoelting 8eBarash 9eFaust

An unsecured aneurysm can rebleed: about 10% to 23% within 2 weeks, about 6% within 24 hours, with mortality over 50%. Early coiling or clipping removes this risk, which is why Miller and the AHA guideline both advise treatment within a day. The Mayo review calls vasospasm the major killer, but refers to patients who survived the first bleed. Once the aneurysm is secured, delayed ischaemia becomes the main threat; before that, rebleeding is the greater danger.

Vasospasm tempts but rebleeding kills first. Vasospasm is tempting because one review calls it the major cause of death, and it is a leading cause of delayed morbidity and mortality in survivors. But in a patient admitted after the bleed, rebleeding from the unsecured aneurysm is the main killer, with mortality over 50%.

Miller names rebleeding as the main cause of death among hospitalised SAH patients. Barash reports that 10% to 23% of unsecured aneurysms rebleed within 2 weeks, with mortality over 50%. The AHA recommends treating the ruptured aneurysm, preferably within 24 hours.

Sources: Miller 10eBarash 9eOutside our books: 2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association (2023)Mayo review

The abnormal vessels of an AVM can bleed when blood pressure rises abruptly. Direct laryngoscopy and passing a tube through the larynx are strong sympathetic stimuli that cause hypertension and tachycardia. A laryngeal mask sits above the glottis and needs no laryngoscope, so induction and emergence cause smaller haemodynamic swings. If intubation is needed, blunt the response with adequate anaesthetic depth, a short-acting opioid or lidocaine, and have arterial pressure control ready in case of bleeding.

Rapid sequence still triggers pressor response. Rapid sequence induction sounds like the safest, most controlled way to secure the airway. But it still depends on direct laryngoscopy and tracheal intubation, which is the stimulus that drives the pressor surge. The patient has no stated aspiration risk that would justify it.

The textbooks say hypertension from laryngoscopy could, in theory, rupture an AVM and should be prevented. A laryngeal mask avoids direct laryngoscopy, so it causes fewer haemodynamic changes than a tracheal tube at insertion, induction and emergence.

Sources: FaustMiller 10eBarash 9e

The unsecured aneurysm lies under a loose, poorly organised clot, so a sudden rise in pressure can make it bleed again. The arterial line shows each beat, so surges are seen at once, ideally from before induction. During the procedure heparin is given at intervals. Clotting tests are therefore repeated, and the arterial line makes repeated sampling easy. Any movement during microcatheter work is dangerous. For that reason the patient is kept still under general anaesthesia with neuromuscular block, rather than under sedation.

Sedation tempts but aneurysm needs immobility. Sedation is tempting because some endovascular work is done lightly sedated, such as embolising malformations in eloquent brain, where the patient can be tested neurologically. For aneurysm coiling the sources say to use general anaesthesia with relaxation, because movement must be prevented.

Barash states coiling requires general anaesthesia with muscle relaxation to prevent movement, and an arterial catheter for close pressure monitoring and repeated clotting samples during heparin administration. Miller calls an arterial line invariably appropriate; Stoelting calls it essential.

Sources: Barash 9eMiller 10eStoelting 8e

A temporary clip stops direct inflow through the parent artery. The territory beyond it then depends on collateral channels, and flow through them falls when perfusion pressure falls. So pressure is lifted to the top of the patient's normal range for the whole occlusion. Once the aneurysm is secured, rupture is no longer the worry, so hypertension control can relax to systolic below 160 mm Hg. Labetalol or esmolol do this well. Nitroprusside is a poor postoperative choice because it raises intracranial pressure and carries a cyanide risk.

Tight ceiling inadequate for collateral flow. A tight ceiling seems safe because rupture of the unsecured aneurysm is the feared event. But during temporary occlusion the brain needs high-normal pressure for collateral flow, and once the aneurysm is secured the target relaxes to systolic below 160 mm Hg.

Stoelting advises keeping pressure near the top of the patient's usual range while the feeding vessel is clamped, to promote collateral flow. Once the aneurysm is excluded, systolic below 160 mm Hg using labetalol or esmolol is reasonable. Nitroprusside raises intracranial pressure.

Sources: Stoelting 8e

Much of the poor outcome after aneurysm rupture comes from delayed cerebral ischaemia. Nimodipine reduces this ischaemia and improves functional recovery. The benefit is thought to come from an effect on the cells, not from widening the spastic arteries. Other calcium-channel blockers do ease vasospasm, but patients do no better with them. So nimodipine is given to every patient from diagnosis, before any spasm appears, and continued through the vasospasm window. It is not held back until spasm is proven, and a different blocker is not a substitute.

Nicardipine tempts but lacks outcome benefit. Nicardipine is a closely related dihydropyridine that is often given intravenously in neurocritical care, so it looks interchangeable. It can reduce vasospasm, but reducing spasm is not the same as improving outcome. Only nimodipine has shown the outcome benefit.

Current stroke guidelines advise starting enteral nimodipine early to prevent delayed ischaemia and improve functional outcome. Textbooks advise starting at diagnosis in every patient, 60 mg orally every 4 hours for 21 days; other calcium-channel blockers do not improve outcome.

Sources: Outside our books: 2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association (2023)Miller 10eFaust

Flow through narrowed cerebral vessels depends on driving pressure. Triple-H therapy (hypertension, hypervolaemia, haemodilution) was the traditional response. Stoelting and Faust now describe it as abandoned because fluid loading and dilution cause pulmonary oedema that worsens outcome. The current AHA guideline therefore targets euvolaemia, not overload. Volume depletion is harmful too: more than half of depleted patients developed delayed ischaemia. What remains of triple-H is the pressure arm: prevent hypotension and let pressure stay high. Enteral nimodipine is added.

Low CVP breeds delayed ischaemic worsening. A low CVP target feels modern because hypervolaemia is now known to harm. But aiming for a low filling pressure pushes the patient towards volume depletion, which itself breeds delayed ischaemia. The goal is euvolaemia, and CVP alone cannot reliably judge volume status anyway.

Stoelting notes that triple-H has given way to hypertension alone with euvolaemia, because overload and dilution complications worsen outcome. Faust lists preventing hypotension and hypovolaemia, plus nimodipine. The AHA guideline targets euvolaemia rather than hypervolaemia and warns that CVP alone misjudges volume.

Sources: FaustStoelting 8eOutside our books: 2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association (2023)

Evoked responses are read against the patient's own baseline. Ischaemia, compression or transection of the pathway makes the response smaller and later, or abolishes it. Faust gives the percentage rule for SSEPs. Miller lists a separate threshold for each modality and treats each as a trigger to alert the team: for brainstem auditory responses, a 0.5 ms rise in wave V latency. The sources do not conflict, as each threshold applies to a different modality. Brainstem auditory responses test the auditory nerve; the facial nerve is monitored with EMG.

Brainstem potentials test auditory nerve VIII. Brainstem potentials are used in acoustic neuroma surgery, where the facial nerve is at risk, so linking them to CN VII feels natural. In fact they test the auditory pathway, which is CN VIII. Facial nerve injury is detected by EMG of the muscles it supplies.

Faust: halved SSEP amplitude or latency prolongation over 10% is significant; pathway ischaemia or injury gives reduced, delayed or absent signal. Miller gives modality-specific alert thresholds, including 0.5 ms wave V latency increase for BAER. BAER monitors CN VIII; EMG monitors CN VII.

Sources: FaustMiller 10e

When cerebral blood flow cannot meet demand, the brain extracts more oxygen per unit of blood. The arteriovenous content gap widens, so jugular bulb blood is less saturated. Miller puts normal at 55–75% and defines saturation below 50% held for 5 minutes as desaturation, linked to poor outcome. Barash calls below 55% critical and aims to stay above it. These fit together: Barash's threshold is the lower edge of Miller's normal range, acting as an early alarm. Values below 50% are the accepted ischaemic cut-off.

55% normal limit not ischaemic threshold. This is tempting because Barash calls saturation below 55% critical desaturation and links it to cerebral ischaemia. It fails because 55% is the lowest value of Miller's normal range and is used as a target to stay above. The accepted ischaemic threshold is below 50%.

Miller gives a normal range of 55–75%. It treats values under 50% lasting 5 minutes as desaturation, meaning inadequate delivery or excess consumption. Barash calls values below 55% critical desaturation, which may reflect ischaemia during hypotension or raised intracranial pressure.

Sources: Miller 10eBarash 9e

Cooling slows neuronal work steadily, cutting cerebral metabolic rate by 6–7% per degree, so electrical activity fades until the EEG goes flat; Miller's physiology chapter and the Mayo review put this near 18–20 °C. Miller's monitoring chapter and Faust show a spread rather than a switch: subjects vary, silence is usually complete by 15–18 °C, and across 14.1–20 °C the share silent rises from 20% to 80% with depth. Unlike anaesthetic drugs, cooling past the flat point still lowers metabolism.

High twenties hypothermia not yet silent. A temperature in the high twenties Celsius sounds right because some classifications mark it as profound hypothermia, where the brain tolerates long periods without flow. But the EEG is not yet silent at that point. Moderate cooling above 20 °C buys some arrest time without reliable electrical silence.

Miller's physiology chapter gives complete EEG suppression at about 18–20 °C, with metabolism still falling on further cooling. Its monitoring chapter notes marked variability between subjects and usual complete suppression at 15–18 °C. Faust reports silence in 20–80% of patients between 14.1 and 20 °C.

Sources: Miller 10eFaust

SSEPs run through the dorsal columns, so when drug levels and physiology are unchanged, a lost signal means the pathway itself is being injured, usually by compression, distraction, derotation or ischaemia, and that injury may recover only if corrected quickly. Systemic factors behave differently: cooling slows conduction and lengthens latency rather than abruptly erasing the trace; neuromuscular blockers spare SSEPs and remove muscle artefact. Alongside, never instead of, surgical correction, optimise cord perfusion: haemodynamics, anaemia, temperature, pH and carbon dioxide.

Cooling misleads about sudden SSEP loss. Cooling is a genuine SSEP modifier, so it looks like a textbook answer. But hypothermia slows conduction progressively and mainly lengthens latency; a mild fall in temperature does not abruptly abolish the signal. A sudden loss during cord manipulation points to the surgeon, not the thermometer.

If anaesthesia and physiology are stable, loss of SSEPs or MEPs signals structural cord damage from compression, distraction, derotation or ischaemia, which can reverse if corrected promptly. Hypothermia slows neural conduction, and muscle relaxants can help by removing spontaneous EMG artefact.

Sources: Miller 10eFaustBarash 9e

Volatile agents suppress cortical signal generation in proportion to dose, so cortical waves are delayed and smaller. This is a class effect shared across the potent inhaled agents. Subcortical, cervical and peripheral recordings are far more resistant to anaesthetic inhibition, so they stay readable at doses that blunt cortical waves. At comparable depth, propofol and other IV agents alter SSEPs much less than volatiles. That is why the choice of anaesthetic matters most when cortical responses are the ones being relied upon.

Sevoflurane still depresses SSEP like others. Sevoflurane is often thought of as the kindest volatile for monitoring, so leaving it out sounds believable. It is wrong because depression of cortical SSEPs is a class effect. Every potent volatile, sevoflurane included, lengthens latency and lowers amplitude in a dose-dependent way.

Standard texts say all volatile agents dose-dependently prolong latency and reduce amplitude of cortical, but not subcortical, SSEPs. Subcortical and peripheral signals resist anaesthetic inhibition. Propofol and other IV agents change SSEPs significantly less than equipotent volatile doses.

Sources: Mayo reviewMiller 10eBarash 9e

Cooling impairs axonal function, so evoked signals arrive later. A core textbook states that hypothermia lengthens SSEP latency. One outside source adds that even slight temperature falls delay it. Mild acidaemia does little: outside sources put the threshold for evoked-potential change below pH 7.2. Neck flexion alters signals only when extreme, by stretching or compressing neural structures. That point comes from one outside source, and the textbooks do not rank it against cooling.

Mild acidosis does not prolong latency. Acidosis does disturb evoked potentials, and the pH here is below normal, so it looks relevant. However, the effect appears only with much more severe acidaemia, and this value is well above that threshold. By contrast, even slight cooling is described as lengthening latency.

A core textbook says hypothermia lengthens SSEP latency. The rest comes from outside the textbooks. One source says even small temperature drops delay latency. Evoked potentials change only below pH 7.2. Extreme neck flexion alters them through stretch or compression.

Sources: Outside our books: Evoked Potentials: Alarm Criteria, Differential Diagnosis, and Recommendations (2026)Faust

The motor tracts in the anterior cord rely on the anterior spinal artery. Much of that supply comes from a radicular feeder, the artery of Adamkiewicz, which arises at a variable level. Clamping the aorta above its origin, or losing it, can leave a large length of cord ischaemic. Sensory potentials run in the dorsal columns and can stay normal while motor pathways fail. Motor potentials close that gap, so recording both catches more cord injury and misses fewer deficits.

Femoral line measures pressure not function. A femoral line shows distal pressure below the cross-clamp, so it looks like a way to protect the cord. It only measures pressure. It cannot show whether the cord is actually working or whether an important feeding artery has been lost. Evoked potentials test cord function directly.

Many centres monitor for cord ischaemia with sensory or motor evoked potentials. Occluding the aorta above the artery of Adamkiewicz endangers much of the cord. Motor deficits can follow normal sensory signals, so recording both raises sensitivity and reduces false negatives.

Sources: Miller 10eFaust

Each component records the best response to escalating stimuli: command or voice, then pain. Eyes: 4 spontaneous, 3 to speech or command, 2 to pain, 1 none. Verbal: 5 oriented, 4 confused, 3 inappropriate words, 2 incomprehensible sounds or moaning, 1 none. Motor: 6 obeys, 5 localises, 4 withdraws, 3 abnormal flexion, 2 extension, 1 none. Withdrawal is a purposeful pull away from the stimulus; abnormal flexion is stereotyped decorticate posturing. Mouth opening and reflexes are not components, so the floor is 3 and the ceiling 15.

Flexor posturing scores 3 not withdrawal. Flexor posturing mimics withdrawal, tempting 1+2+4 (6+1). Posturing is abnormal flexion scoring 3, not withdrawal 4 or extension 2, so no eye opening, moaning and posturing give 1+2+3=6. True withdrawal from a needle gives that total; eyes to command, sounds and localising give 3+2+5 (6+4).

The score sums the best eye, verbal and motor responses, capped at 4, 5 and 6, giving 3 to 15. The table separates withdrawal, 4, from abnormal flexion, 3, and grades incomprehensible sounds 2 and no eye opening 1.

Sources: Mayo reviewStoelting 8e

The scale depends on sacral sparing. S4–5 are the lowest cord segments. If any sensation or movement survives there, some tracts still cross the lesion, so the injury is incomplete. If both are absent there, the injury is complete: grade A. An incomplete injury with sensation but no motor function is B. Once some motor function survives, strength decides: if more than half the key muscles below the level score under 3, it is C; otherwise it is D. Normal motor and sensory function is E.

A means complete loss not best. The letter A sounds like a top mark, so people assume it means the best function. The scale runs the other way. A is a complete loss of motor and sensory function, and a cord with intact function is graded E.

The textbooks and the international standard agree on the grades. A is complete, with no motor or sensory function, including the lowest sacral segments. B to D are incomplete, with sacral sparing. C is when most key muscles score under 3. E is normal.

Sources: Barash 9eMiller 10eOutside our books: International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019 (2021)

The grade measures how badly the bleed has injured the brain, judged at the bedside from consciousness and motor signs. Headache, or a cranial nerve palsy alone, means limited injury. Mortality rises sharply once consciousness falls to stupor with hemiparesis, and it is highest with coma and rigidity. Stoelting tabulates mortality by grade. Miller tabulates survival by grade, a separate outcome, and gives 20% for grade 4. The two columns measure different things, so a mortality question takes Stoelting's figures.

20 survival rate not mortality. 20 is tempting because a major text prints 20 beside grade 4. That column is survival, not mortality, so reading it as a death rate turns its meaning upside down. Stoelting's mortality for grade 4 is 25–30%, so 30 is the answer.

Mortality by grade: 0 unruptured aneurysm 0–2%; 1 minimal headache, no deficit 2–5%; 2 moderate–severe headache, cranial nerve palsy 5–10%; 3 drowsy, confused or mild focal motor deficit 5–10%; 4 stupor with significant hemiparesis or early decerebration 25–30%; 5 deep coma with decerebrate rigidity 40–50%.

Sources: Stoelting 8eMiller 10e

Leventhal's 1980 score weights each predictor. Long-standing disease scores highest because it marks established weakness. Non-myasthenic lung disease removes respiratory reserve. A high pyridostigmine requirement signals poorly controlled disease. Low vital capacity reflects weak respiratory muscles. Duration alone (12) or lung disease alone (10) reaches the threshold; pyridostigmine (8) or vital capacity (4) needs a second factor. Miller's says the score now matters less because of better preparation and minimally invasive surgery, so treat it as a risk flag, not a certainty.

Vital capacity measures respiratory muscle strength. First-second forced expiratory volume is the usual marker of obstructive lung disease and general pulmonary risk, so it seems the right test. In myasthenia, risk depends on respiratory muscle strength, which vital capacity measures. Coexisting lung disease is scored from the history, not from that value.

Leventhal's 1980 score gives 12 points for disease beyond 72 months, 10 for respiratory disease, 8 for pyridostigmine above 750 mg/day and 4 for vital capacity below 2.9 L. A total of 10 or more predicted prolonged intubation. Miller's says its relevance has since diminished.

Sources: Outside our books: Thymectomy in myasthenia gravis: proposal for a predictive score of postoperative myasthenic crisis (2014)Barash 9eMiller 10e

Coma is loss of arousal itself: the brainstem–thalamic arousal system or both hemispheres fail, so the eyes stay shut, sleep-wake cycling is lost and stimuli draw only reflexes; Stoelting defines only coma. Outside the textbooks, StatPearls adds the others: in vegetative state arousal returns, so the eyes open, but awareness of self and surroundings is absent; in locked-in syndrome a pontine lesion paralyses body and bulbar muscles while cognition survives, leaving vertical gaze and blinking to communicate. Breathing pattern does not separate them.

Open eyes without awareness vegetative state. The word unconscious pulls towards coma, but coma needs closed eyes and no sleep-wake cycling. Open eyes with no awareness or purposeful movement mean arousal has returned without content, which is vegetative state. Locked-in is ruled out because that patient is fully aware.

Stoelting defines coma as lost arousal with closed eyes, no sleep-wake cycles and reflex-only responses. Outside the books, StatPearls describes vegetative state as eye-opening without awareness, and locked-in syndrome as preserved cognition, vertical eye movement and blinking.

Sources: Stoelting 8eOutside our books: Locked-in Syndrome (2026)

An alert cortex produces fast, low-amplitude, desynchronised beta activity, and alpha appears when the eyes close. When the brain is depressed by sleep, drugs or injury, the thalamocortical network becomes progressively hyperpolarised. Its rhythms then slow and grow in amplitude: theta (4 to 8 Hz) comes first, then delta (0.5 to 4 Hz). A delta-dominant trace marks the deepest synchronised state and resembles deep slow-wave sleep. Only burst suppression and a flat trace lie beyond it. Alpha coma is a separate malignant pattern seen after anoxic injury.

Theta intermediate not slowest deep coma. Theta is a slow rhythm and does indicate a depressed brain, so it seems a natural answer for coma. But it is an intermediate band that appears in lighter depression. As depression deepens, the rhythm keeps slowing past theta until delta, the slowest band, dominates.

Theta and delta activity both indicate a depressed brain. Deep sleep and anaesthesia both slow the EEG into the theta and then the delta band. When delta takes over from alpha, the thalamocortical system is more deeply hyperpolarised, as in deep slow-wave sleep.

Sources: Mayo reviewBarash 9eMiller 10e

Brain death is permanent loss of both cerebral and brainstem function. Every reflex arc that runs through the brainstem therefore stays silent. These include the pupil's response to light, the corneal blink, eye movement after ice-water ear irrigation, gag, cough and the breathing response to rising carbon dioxide. The spinal cord can still work, and its reflex loops are self-contained, so withdrawal or complex limb movements may appear. Such movements fit the diagnosis. If their origin is uncertain, add an ancillary test. During organ retrieval, neuromuscular blockade may be needed.

Corneal reflex brainstem not spinal. People know some reflexes survive brain death and may think the corneal reflex is one of them. It is not. The corneal reflex is a brainstem reflex, not a spinal one, so any corneal response rules out brain death. The guideline requires it to be absent on both sides.

Brain-dead patients lack all brainstem reflexes, including respiratory drive, though spinal or peripheral nerve movements may persist and may need paralysis at procurement. The guideline classes pupillary and corneal reflexes as brainstem reflexes; corneal responses must be absent bilaterally.

Sources: Barash 9eOutside our books: Pediatric and Adult Brain Death/Death by Neurologic Criteria Consensus Guideline: Report of the AAN Guidelines Subcommittee, AAP, CNS, and SCCM (2023)

Each prerequisite rules out something reversible that can look like brainstem death. Cold slows the clearance of drugs that depress the brain. Low blood pressure can itself suppress brain function. Either can produce areflexia and apnoea and give a false-positive diagnosis. The apnoea test asks whether rising CO2 drives breathing, so it must start from a normal PaCO2 in a stable, euvolaemic, well-oxygenated patient. Stoelting gives the CO2 target and the need for stability. The temperature and blood pressure thresholds come from the AAN brain death guideline, an outside source.

PaCO2 prerequisite not oxygen saturation. It is tempting because the patient must be well oxygenated before the ventilator is disconnected. But no source makes a particular oxygen saturation the prerequisite. The defined starting condition is a normal PaCO2, because the test measures whether the respiratory centre responds to rising CO2.

Stoelting advises apnoea testing in a haemodynamically stable, euvolaemic patient once PaCO2 is 40 ± 5 mmHg with adequate oxygenation. The AAN guideline (external source) requires core temperature ≥36 °C and no hypotension, citing the earlier systolic threshold of ≥100 mmHg.

Sources: Stoelting 8eOutside our books: Pediatric and Adult Brain Death/Death by Neurologic Criteria Consensus Guideline: Report of the AAN Guidelines Subcommittee, AAP, CNS, and SCCM (2023)

Deltoid and biceps each receive C5 and C6 fibres, as Stoelting's table shows, so either root can weaken them. Barash and the spinal-injury examination standard instead treat C5 as the defining segment for deltoid, biceps, brachialis and brachioradialis. A radiculopathy table resolves the overlap. A C5 root lesion weakens the deltoid and depresses the biceps reflex. A C6 lesion adds wrist-extensor weakness and a depressed brachioradialis reflex. So loss of shoulder abduction or a lost biceps reflex fixes the level at C5.

C5 supplies deltoid and biceps reflex. C6 tempts because biceps carries C6 fibres and the brachioradialis reflex is a C6 marker. But the radiculopathy table assigns deltoid weakness and the biceps reflex to C5. A true C6 lesion should also weaken wrist extension.

Stoelting attributes deltoid and biceps to C5 and C6. Barash and the injury-classification standard identify C5 as key for elbow flexors (biceps, brachialis). The radiculopathy table links deltoid weakness and biceps reflex to C5, wrist-extension weakness and brachioradialis reflex to C6.

Sources: Barash 9eOutside our books: Cervical Radiculopathy (2016)Stoelting 8eOutside our books: International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019 (2021)

Cervical roots exit above their same-numbered vertebra, so a C6-7 disc compresses C7 and a C5-6 disc C6; this mapping comes from outside the textbooks. The spinal injury standard names triceps the key C7 muscle, while Stoelting's table gives its full supply as C6 to C8: key segment versus total supply, not a conflict. C7 is the commonest root, and at surgery reflex and motor signs matched the level more often than sensory ones, so thumb pain with triceps weakness still favours C6-7; C5-6 is defensible.

Triceps C7 sign beats sensory localisation. Thumb pain maps to the C6 dermatome, so a C5-6 disc looks right. But triceps is the key C7 muscle, C7 is the commonest root, and the sensory site localises the level least reliably, so the motor sign wins; C5-6 remains defensible.

A radiculopathy review tabulates C7 as triceps weakness, middle-finger pain and a reduced triceps reflex, reports C7 from a C6-7 disc as the commonest, and found reflexes and weakness matched surgical level more often than sensory loss; the injury standard tests triceps for C7.

Sources: Outside our books: Cervical Radiculopathy (2016)Outside our books: International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019 (2021)

The knee jerk is a quadriceps reflex, and Stoelting gives the quadriceps a femoral supply from L2, L3 and L4, so a weak reflex fits L3 or L4. The spinal-injury standard places L3 at the medial knee and L4 at the medial malleolus. Thigh maps differ: the Keegan and Garrett disc-herniation map starts L4 on the lateral thigh, while older maps, outside the textbooks, give that strip to L2 and L3. Below the knee all agree: medial shin and malleolus are L4, dorsum of foot L5. Read the leg.

L3 because it supplies quadriceps. L3 does supply the quadriceps, so a lost knee jerk invites L3. But L3 skin covers the medial thigh and ends at the knee; numbness crossing onto the medial shin is L4 on every map. Lateral-thigh numbness alone cannot decide; older maps call it L2 or L3.

Stoelting gives the quadriceps a femoral supply from L2–L4. StatPearls: L4 is the commonest lumbosacral disc level, with medial lower-leg numbness and reduced patellar reflex. Dermatome review: L4 runs from lateral thigh over knee to medial malleolus; ISNCSCI keys L3 above the knee.

Sources: Stoelting 8eOutside our books: Electrodiagnostic Evaluation of Lumbosacral Radiculopathy (2025)Outside our books: Surface Anatomy and Sensory Evaluation of Dermatomes: A Guide for Residents (2025)Outside our books: International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019 (2021)

At the wrist, the median nerve runs through a tight tunnel. The carpal bones form its floor and the transverse carpal ligament forms its roof. Anything that narrows this space compresses the nerve. Symptoms follow its sensory territory: the thumb, index finger and middle finger. The ulnar nerve and the radial nerve do not pass through this tunnel, so they are not affected.

Carpal tunnel purely median nerve only. The radial nerve supplies skin on the back of the thumb, so a mixed answer looks careful. It is wrong because carpal tunnel entrapment affects only the median nerve. Symptoms in the three lateral digits come from that one nerve.

Recurrent wrist and hand pain and paraesthesia follow the median nerve (thumb, index, middle fingers). Compression occurs at the wrist, between the transverse carpal ligament and carpal bones. Otherwise healthy women are most affected, three times more than men.

Sources: Stoelting 8e

Damage to one half of the cord cuts the motor and dorsal column pathways of that side. Those tracts stay on their own side until the brainstem, so the patient loses power, joint-position sense and vibration on the injured side. Pain and temperature fibres cross to the opposite side close to where they enter the cord. So the same half-cord lesion removes pain and temperature sensation from the other side of the body. The result is a weak limb on one side and a numb limb on the other.

Contralateral pain loss indicates hemisection only. Central cord injury is the best-known incomplete syndrome, and real patients often mix its features with a hemisection picture. But it does not split cleanly by side. A weak limb on one side with loss of pain and temperature on the other points to a one-sided lesion.

Hemisection of the cord gives loss of motor control, proprioception and vibration on the same side at and below the lesion, with loss of pain and temperature on the opposite side. The pure form is uncommon, and mixed presentations are more usual.

Sources: FaustOutside our books: International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019 (2021)

Cranial nerve nuclei in the brainstem supply the face on their own side. The corticospinal fibres to the limbs pass through the brainstem before they cross in the lower medulla. So one brainstem lesion weakens the face on the same side and the limbs on the opposite side. A lesion above the brainstem, in the cerebral hemisphere, affects fibres that have not yet reached either crossing point. That gives facial and limb deficits together on the side opposite the lesion.

Right stroke weakens right face too. The left-sided limb signs point to a right-sided lesion, so a right-sided vessel looks right. But a right hemispheric stroke would weaken the left face too, not the right. The posterior cerebral artery mainly causes a contralateral visual field defect, not crossed signs.

The textbook table of regional stroke syndromes links basilar artery strokes to eye-movement problems or ataxia with crossed motor and sensory signs. It links vertebral artery strokes to lower cranial nerve deficits with crossed sensory signs. Hemispheric and penetrating-vessel strokes cause one-sided contralateral weakness.

Sources: Stoelting 8e

Below the end of the cord, the cauda equina is a bundle of lumbosacral roots. These roots are lower motor neurons, so injuring or compressing them produces flaccid, areflexic leg weakness and an areflexic bladder and bowel. Sensory loss affects the saddle area, and the anal wink and bulbocavernosus reflexes disappear. In anaesthesia, spinal local anaesthetic pooling unevenly in dependent parts of the subarachnoid space is a recognised cause.

Guillain-Barré lacks acute sphincter saddle loss. Guillain-Barré also gives bilateral flaccid leg weakness, so it looks like a fit. But abrupt, combined bowel and bladder failure with saddle sensory loss points to a focal lumbosacral root lesion, not a diffuse ascending polyneuropathy.

The features are back pain, weakness in both legs, saddle anaesthesia and loss of sphincter control. Root injury gives flaccid lower-limb paralysis, an areflexic bowel and bladder, and absent sacral reflexes. Local anaesthetic pooling within the subarachnoid space has been implicated.

Sources: Mayo reviewOutside our books: International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019 (2021)

Breathing rhythm is generated in the brainstem. The pons normally ends inspiration; if injured, inspiration is not switched off on time, so the patient holds the breath at full inspiration, then releases it in gasps (apneustic breathing). The medulla generates the basic rhythm; if injured, timing breaks down, giving random rates and depths (ataxic, or Biot, breathing). A cyclic waxing and waning pattern points higher, to the cerebral hemispheres.

Held gasped breathing indicates pontine injury. Venous air embolism is the complication most associated with posterior fossa surgery, but it presents with impaired gas exchange and circulation, not a set breathing pattern. Breath held at full inspiration and released in gasps is a specific sign of pontine injury.

A table of abnormal breathing patterns ties each one to a lesion site. Apneustic breathing (gasps, long pauses at full inspiration) means the pons. Ataxic or Biot breathing (irregular breaths that vary in rate and depth) means the medulla. Cheyne-Stokes breathing means the cerebral hemispheres.

Sources: Stoelting 8e

A preceding viral or bacterial infection triggers antibodies that mistake gangliosides on peripheral nerves for the microbe (molecular mimicry). The delay reflects the time the antibody response takes to build. The attack falls on spinal roots and peripheral nerves, causing flaccid, symmetrical weakness with reduced or absent reflexes. It usually starts in the legs and spreads upwards; sensory symptoms may or may not be present. The target is the lower motor neuron pathway, not the kidney, heart muscle or brain.

Autonomic dysfunction nerve-based not cardiac. Autonomic dysfunction is a recognised GBS feature, so heart-rate and blood-pressure instability make a cardiac answer look plausible. But that is dysautonomia from nerve involvement, not heart muscle disease, and it is not what announces the illness: the disease targets roots and peripheral nerves, so limb weakness comes first.

GBS is an immune-mediated acute polyradiculopathy. It causes fast, ascending, symmetrical limb weakness with reduced reflexes. Symptoms typically begin 1 to 6 weeks after a respiratory or gut infection, starting in the lower limbs. Anti-ganglioside autoantibodies drive the disease.

Sources: Miller 10eBarash 9e

Antibodies against presynaptic calcium channels reduce calcium entry, so each impulse releases too little acetylcholine. Repeated firing lets calcium accumulate in the terminal, so strength climbs with exercise and as the day progresses. This is the opposite of myasthenia gravis, where use worsens weakness. Autonomic features like dry mouth also favour it. Most texts say legs are hit more; one comparison table lists arms more. Either way it is proximal, and the response to use decides.

Improvement with use suggests Lambert-Eaton. Myasthenia gravis shares fatigable weakness and the 'myasthenic' label, so it feels right. But its weakness worsens with exercise and favours eye, bulbar and facial muscles. Improvement with use, autonomic upset and a smoker's lung tumour point instead to a presynaptic release defect.

The texts describe an antibody-driven presynaptic release defect linked to small cell lung tumours. It causes proximal weakness that improves with exercise and through the day, often with autonomic dysfunction, and responds poorly to anticholinesterases. Myasthenia gravis instead weakens with exercise.

Sources: Barash 9eStoelting 8eMiller 10e

The fault is presynaptic. Each nerve impulse releases too little acetylcholine, while the number of postjunctional receptors stays normal. Because transmission already has a thin margin, any relaxant tips the junction into failure, whether it blocks receptors or depolarises them. Both classes therefore act more strongly than expected. Myasthenia gravis is different: it loses receptors, which makes suxamethonium less effective. In Lambert-Eaton, repeated firing lets transmitter release build up, so strength improves with exercise and EMG amplitude grows. Anticholinesterases help little because the problem is acetylcholine supply, not its breakdown.

Defective release causes suxamethonium sensitivity. People carry over the myasthenia gravis pattern, where fewer receptors make resistance to suxamethonium the rule, and so mark sensitivity to depolarisers as false. In Lambert-Eaton the receptors are normal and the defect is in transmitter release, so these patients are sensitive to suxamethonium as well as to non-depolarisers.

Two anaesthesia texts list Lambert-Eaton as sensitive to both relaxant classes, commoner in men, with frequent muscle pain, reduced reflexes, small-cell lung carcinoma and a poor response to anticholinesterases. A review blames reduced acetylcholine release with normal receptor numbers. EMG amplitude increases on repeated stimulation.

Sources: Mayo reviewBarash 9eMiller 10eStoelting 8e

Delivery does not treat the disease: registry data put the risk of onset lowest during pregnancy and two to three times higher the month after delivery, and postpartum relapse is described. An older case-report view held that it reliably worsens after birth; cohort data do not bear that out, so treat the puerperium as the riskiest window, not a certain decline. It is immune-mediated and symmetrical. Immunoglobulin and plasma exchange are safe in pregnancy; recovery is often incomplete. Miller calls regional controversial; Barash says it is still common in labour.

Delivery brings relief. The first half is right: onset clusters late in pregnancy. The second half fails: delivery brings no relief. The weeks after birth are the period of highest risk for onset and for relapse, so the postpartum weeks need closer watching, not reassurance.

Outside the textbooks, case reports with literature reviews cluster pregnancy cases in the third trimester and first 2 weeks postpartum and describe postpartum worsening. Miller: immune-mediated, symmetrical ascending weakness; regional controversial. Barash: still commonly used in labour.

Sources: Outside our books: Guillain-Barre syndrome in pregnancy: A conservatively managed case (2016)Miller 10eBarash 9e

Hyponatraemia after subarachnoid haemorrhage has two causes. In SIADH, retained free water dilutes sodium despite normal volume. In cerebral salt wasting, sodium and water loss shrinks circulating volume. Barash teaches water restriction for SIADH and volume and sodium for salt wasting. After a bleed, however, a contracted circulation worsens cerebral vasospasm, so Miller warns against restriction and treats either cause with isotonic or hypertonic fluid. As the two are hard to distinguish at the bedside, saline is safe for both.

Low volume means salt wasting here. Removing free water sounds like the right fix for a dilutional low sodium, because it is the classic SIADH treatment. This patient is dry, though: a low CVP and a raised haematocrit point to salt wasting. Losing more volume after a bleed aggravates vasospasm.

Barash says water restriction is for SIADH, while salt wasting needs volume and sodium replacement. Mayo notes that hypovolaemia worsens vasospasm, the main killer after this bleed. Miller advises against restriction after the haemorrhage and gives isotonic or hypertonic fluid whichever the cause.

Sources: Barash 9eMayo reviewMiller 10e

ADH keeps acting even though the plasma is already dilute, so the kidney holds on to free water. Plasma sodium and osmolality fall while the urine stays concentrated. The retained water keeps the circulation full, slightly overfull at most, so sodium carries on being excreted. The Mayo review calls the blood volume expanded and elsewhere calls CVP relatively normal. Barash's phrase, euvolaemia or mild hypervolaemia, covers both. Filling is normal to high, never low. Salt wasting is different: sodium is lost first, water follows, and the patient becomes volume-depleted.

Volume status distinguishes salt wasting. The blood and urine results match SIADH exactly, and high urine sodium feels like its signature. But urine sodium is high in cerebral salt wasting too. Only volume status separates the two conditions. A low filling pressure means volume contraction, which points to salt wasting rather than water retention.

The sources describe SIADH as low serum sodium and osmolality with high urinary sodium and osmolality. Volume is normal or slightly increased because water is retained. Cerebral salt wasting has the same low serum sodium and high urine sodium, but with volume contraction.

Sources: Mayo reviewOutside our books: Perioperative management of endoscopic transsphenoidal pituitary surgery (2020)Barash 9eMiller 10e

Injury around the hypothalamus or posterior pituitary stops antidiuretic hormone from reaching the kidney. Without it, the collecting ducts cannot reabsorb free water, so large volumes of dilute urine are passed. More water than sodium is lost, so the plasma becomes concentrated and sodium rises. This happens faster if the patient cannot drink. SIADH is the opposite: too much hormone holds on to water and dilutes sodium. After suprasellar surgery these phases can alternate, so the urine pattern at the time shows which way sodium is moving.

SIADH confusion; hyponatraemia not hypernatraemia. Low sodium is the electrolyte problem most linked with brain insults, through SIADH and cerebral salt wasting, so it comes to mind first. But SIADH retains water and does not cause dilute polyuria. Losing free water in dilute urine concentrates the plasma, so sodium rises.

Loss of antidiuretic hormone causes polyuria of dilute urine with hypernatraemia, whereas SIADH causes hyponatraemia. Diagnosis needs urine below 300 mOsm/kg together with hypernatraemia and serum osmolality above 305 mOsm/kg. After suprasellar surgery the usual sequence is SIADH, then DI, then SIADH again.

Sources: Barash 9eMayo reviewMiller 10e

A major insult such as aneurysmal bleeding triggers release of cortisol, glucagon, catecholamines and growth hormone. These increase hepatic glucose production through gluconeogenesis and glycogenolysis. Glucagon and adrenergic drive also suppress insulin secretion. Inflammatory cytokines amplify the hormone surge and impair intracellular insulin signalling, causing insulin resistance in liver and skeletal muscle. The liver keeps releasing glucose while muscle takes up less, so blood glucose rises even in non-diabetic patients.

Diabetes insipidus causes water loss not glucose. Diabetes insipidus is a well-known complication of intracranial catastrophe, and the word 'diabetes' makes it look linked to glucose. But it is a failure of water handling that causes large urine volumes and a rising sodium. It does not raise blood glucose.

Stress hormones drive hepatic glucose production and glycogen breakdown, and glucagon and adrenergic activity suppress insulin release. Inflammatory mediators disrupt insulin signalling and cause marked insulin resistance. That resistance, in liver and muscle, explains the hyperglycaemia.

Sources: Barash 9eStoelting 8e

Miller explains that SAH triggers a surge in catecholamines and sympathetic tone, and this autonomic storm alters the ECG: T-wave inversion, U waves and a long QT, usually settling within 72 hours. Faust notes that while some of these changes are benign, others may mark myocardial damage, so assess the heart rather than dismiss them. Low calcium also lengthens QT, but Barash calls the ECG insensitive for detecting it, so a coexisting hypocalcaemia does not displace SAH as the expected cause.

Hypocalcaemia mimics but SAH causes QT. A low calcium is reported and hypocalcaemia truly lengthens QT, so it feels like the lab-proven answer. But a long QT is expected after SAH from the sympathetic surge, and the ECG is an insensitive marker of hypocalcaemia, so SAH remains the cause.

Mayo lists T-wave inversion, ST shifts, U waves and QT prolongation after SAH, fading within 72 hours; Miller attributes them to a catecholamine surge. Some are benign, some reflect myocardial damage. Hypocalcaemia also prolongs QT, though the ECG detects it poorly.

Sources: Mayo reviewMiller 10eBarash 9eFaust

When the sac or vessel perforates, blood escapes into the closed skull. Intracranial pressure then climbs abruptly towards arterial systolic pressure, venous outflow slows and cerebral perfusion pressure falls. The patient responds with a Cushing reflex: systemic pressure surges first, then the heart slows, and hypotension may follow. The textbooks describe the separate pieces, with dye leaking into brain as a marker of rupture and the Cushing triad as a marker of raised ICP. Outside neurointerventional sources join the two for the coiling suite.

Vertebral dissection less likely than coil rupture. Tempting when the catheter reaches a basilar aneurysm via the vertebral artery, as dissection with brainstem ischaemia seems plausible. But the change followed coil placement. Hypertension with bradycardia is the Cushing pattern of abrupt ICP rise from rupture. Check the images for extravasated contrast.

Outside the textbooks, a neurointerventional review and OpenAnaesthesia describe intraprocedural rupture as causing contrast extravasation and acute hypertension, then bradycardia, as a Cushing response to rapidly rising ICP. A textbook adds that dye leaking into brain may mean aneurysmal or feeding-vessel rupture.

Sources: Outside our books: Commentary: Endovascular Tamponade of Iatrogenic Vessel Perforation With Temporary Coiling: 2-Dimensional Operative Video (2023)Outside our books: Anesthesia for Neurointerventional Procedures (2026)Barash 9e

The trigger is raised ICP starving the medulla of blood flow, so the vasomotor centre becomes ischaemic. It fires a sympathetic discharge that briefly lifts heart rate, contractility and arterial pressure, trying to force perfusion into the brain against the high ICP. Baroreceptors then sense the high pressure and slow the heart through a parasympathetic reflex. The sign doctors recognise is therefore hypertension with bradycardia, often with irregular breathing. The slowing of the heart is the less dependable part of the pattern.

Baroreceptor causes hypertension not hypotension reflex. Hypotension is tempting because the bradycardia is a baroreceptor reflex, and baroreflexes are usually pictured as responding to falling pressure. In the Cushing reflex the trigger is raised ICP causing medullary ischaemia. Arterial pressure rises, not falls, and the bradycardia is the response to that hypertension.

The reflex is explained as medullary ischaemia from high intracranial pressure causing sympathetic activation, with baroreceptor-mediated bradycardia following. As pressure keeps rising, a triad of hypertension, bradycardia and irregular breathing appears. The heart rate component is less reliable than the pressure rise.

Sources: Miller 10eBarash 9e

Miller's coiling section gives the steps after rupture: neutralise heparin with protamine, 1 mg per 100 units, and bring arterial pressure down. Miller's neurotrauma section adds a branch for herniation. If a Cushing triad appears (hypertension, bradycardia, irregular breathing), hyperventilation on 100% oxygen constricts cerebral vessels and cuts cerebral blood volume. Mayo calls this the fastest way to lower ICP. The two fit together: protamine always, hyperventilation when Cushing signs appear, then control pressure with an agent that spares cerebral vessels. Hydralazine dilates them.

Mannitol slower than hyperventilation for ICP. Mannitol really does lower ICP and is kept ready in this emergency, so it looks just as correct. It loses only on speed. An osmotic agent needs time to shrink the brain, and hyperventilation is the quickest way to bring ICP down in a patient who is herniating now.

Miller advises reversing heparin with protamine (1 mg per 100 units) and lowering arterial pressure after rupture. It calls hyperventilation on 100% oxygen life-saving when a Cushing triad appears. Mayo ranks hyperventilation the fastest ICP reducer. Miller notes hydralazine dilates the cerebral circulation.

Sources: Miller 10eMayo review

Handling the trigeminal nerve root sends a signal in along the trigeminal nerve, and the reflex answers through the vagus, which slows the heart. Take away the stimulus and you take away that drive. The rhythm usually recovers within 20 seconds, provided anaesthetic depth and ventilation are also checked. If a drug is needed because the slowing is serious or keeps coming back, choose atropine. It blocks the vagal output at the heart, so it treats the cause, not just the blood pressure.

Atropine after stimulus removal, not first. Atropine is tempting because it is the right antidote to vagal bradycardia. But if you give it while the surgeon is still pulling on the nerve, the trigger is still there. First remove the stimulus. Atropine comes next, and only if the slowing is severe or returns.

Barash advises asking the surgeon to stop manipulating immediately, then checking anaesthetic depth and ventilation. Rhythm usually normalises within 20 seconds. Reserve atropine for serious or recurrent dysrhythmia. Stoelting notes trigeminal nerve surgery can trigger this reflex bradycardia.

Sources: Barash 9eStoelting 8e

Skull pins, scalp infiltration and incision are noxious and cause a sympathetic surge like laryngoscopy. Adrenaline in the infiltrate is absorbed and raises pressure further; alone it usually speeds the heart. The slow rate is a reflex: baroreceptors detect the abrupt pressure rise and drive vagal outflow. It follows from the hypertension and is not a separate problem. Blunting the stimulus with more propofol, volatile or a short-acting opioid, with esmolol or lidocaine as adjuncts, treats both.

Ventilation changes miss noxious stimulus cause. The low saturation and low end-tidal CO2 are real and call for a quick check of the tube, circuit and ventilation. They did not cause a pressure surge timed exactly to the infiltration. Changing ventilation leaves the noxious stimulus and the absorbed adrenaline untreated.

Head-pin fixation causes a laryngoscopy-like response, controlled with propofol, opioids or esmolol. Deepening with volatile, intravenous agent or short-acting opioid, or giving lidocaine or esmolol, blunts pinning and incision responses. Absorbed adrenaline causes hypertension and tachycardia. Raised pressure triggers baroreceptor-mediated parasympathetic slowing.

Sources: Barash 9eFaustMiller 10eStoelting 8e

Sitting and posterior fossa positions place the wound above the heart. Opened veins that cannot collapse, such as dural sinuses and cut bone edges, keep drawing in air for as long as they stay open. Air collecting in the right heart can form a lock in the ventricular outflow and cause haemodynamic collapse. Only sealing the entry point, with saline, bone wax or cautery, stops the load growing. Oxygen, aspiration through a right atrial catheter, positioning and vasoactive drugs treat only air that has already entered.

Flood field before oxygen, close vein. Oxygen is a real part of treatment. It helps with hypoxaemia and hypotension, and de-nitrogenation shrinks the bubble, so it feels like the reflex answer. But it does nothing to close the open vein. Air keeps entering until the surgeon floods the field, so oxygen comes second.

Surgeon halts air entrainment: flood field with normal saline, may apply bone wax. Give 100% oxygen to treat hypoxaemia or hypotension and shrink the embolus by de-nitrogenation. Consider left-side-down and Trendelenburg positioning to dislodge right ventricular outflow tract air lock. Sitting position carries risk.

Sources: Miller 10eStoelting 8e

Doppler placed over the right heart picks up intracardiac air through the chest wall, so it detects very small volumes, about 0.05 mL/kg, without entering the body. TEE looks at the heart directly and finds even smaller amounts. However, it needs a probe in the oesophagus, is cumbersome and needs a trained observer. That makes it invasive, so it is not the answer when the question says non-invasive. End-tidal carbon dioxide, pulmonary artery catheters and the oesophageal stethoscope are all far less sensitive.

TEE invasive; precordial Doppler is correct. TEE is the most sensitive air detector, so people equating "best" with "most sensitive" choose it. However, the question asks for a non-invasive method, and TEE is invasive, needing an oesophageal probe and skilled operator. Among non-invasive monitors, precordial Doppler is the most sensitive.

Transthoracic Doppler is the most sensitive non-invasive monitor and detects roughly 0.05 mL/kg of air. Doppler is beaten only by TEE, which is more sensitive but cumbersome, invasive and needs a skilled observer. Capnography, pulmonary artery catheters and oesophageal stethoscopes are much less sensitive.

Sources: Miller 10eMayo reviewBarash 9e

After the initial impact, continued cord compression adds a potentially reversible second injury. Laboratory evidence suggests that prompt decompression spares neural tissue and improves recovery. Studies therefore compare early decompression (within 24 hours) with late decompression (after 24 hours). The two sources agree on timing and differ only in certainty. Miller's states the 24-hour target firmly. The AO Spine guideline supports the same timing but gives a weak recommendation based on low-quality evidence. The practical rule is to decompress early, recognising that the evidence is only modest.

24 hours not immediate; evidence-based window. "Immediately" is tempting because the cord is time-sensitive and feels like it needs instant action. But the evidence defines the benefit as decompression within the first 24 hours compared with later. It does not test operating at once, so the target to name is the 24-hour window.

Miller's advises decompressing the injured cord within 24 hours. The AO Spine guideline suggests offering early surgery, defined as within 24 hours, to adults with acute cord injury, including central cord syndrome. It rates this a weak recommendation based on low-quality evidence.

Sources: Miller 10eOutside our books: A Clinical Practice Guideline for the Management of Acute Spinal Cord Injury: Introduction, Rationale, and Scope (2017)

An injury above the upper thoracic segments cuts off sympathetic outflow. Vessels dilate, lowering vascular resistance. The heart loses its accelerator fibres, leaving vagal tone unopposed, so heart rate falls rather than rising to compensate. This haemodynamic picture is neurogenic shock. Spinal shock is a separate, neurological term for absent sensation, movement and reflexes below the lesion. Miller says spinal shock is the wrong term for the circulatory picture, although some reviews loosely include sympathectomy under it. The two often coexist, but the shock type is neurogenic.

Spinal shock differs from neurogenic shock. It is tempting because the patient really does have spinal shock: flaccid weakness and sensory loss below the lesion, and the word 'spinal' matches the injury. But the term describes lost cord function, not circulatory failure. Low blood pressure with a slow heart rate is neurogenic shock.

Miller attributes hypotension after injuries above T4–6 to vasodilatation, reduced inotropy and bradycardia from denervated cardiac accelerator fibres. It calls this neurogenic shock and rejects spinal shock as the term. Spinal shock means abolished sensory, motor and reflex function below the injury.

Sources: Miller 10eOutside our books: Evaluation and Management of Autonomic Dysreflexia and Other Autonomic Dysfunctions: Preventing the Highs and Lows - Management of Blood Pressure, Sweating, and Temperature Dysfunction (2020)

A strong stimulus below the injury triggers spinal sympathetic reflexes the brain can no longer inhibit, so vessels below the lesion constrict and pressure surges; intact baroreceptors drive vagal bradycardia. The surge needs most sympathetic outflow isolated, hence a mid-thoracic cut-off. Stoelting and Faust place it at T6; Barash cites the same 85% for complete lesions above T5, which lie within that group, so the books agree. During cystoscopy under spinal, dysreflexia means the block is inadequate; a sound spinal or general anaesthetic prevents it.

T6 threshold not T5; Stoelting standard. Above T5 is tempting because Barash attaches the familiar 85% figure to complete transection above T5. That describes only a narrower group of higher, complete lesions. Stoelting, Faust and the cord-injury guideline all place the threshold at T6 and describe the wider group at risk.

Stoelting reports roughly 85% incidence with lesions above T6 and calls it unlikely below T10. Faust gives at least two-thirds at T6 or above. Barash quotes 85% after complete transection above T5, once spinal shock has resolved.

Sources: Stoelting 8eBarash 9eFaust

A noxious stimulus below the injury, most often a distended bladder, provokes a reflex sympathetic surge that drives blood pressure sharply upward, while a compensatory vagal response slows the heart. The stimulus itself keeps the surge going, so the crisis usually subsides once the source is removed. The bladder is examined first simply because it is the commonest culprit. Raising the head and loosening clothing buy time while the source is found and relieved.

Relieve bladder urgently, not recheck monitor. Rechecking a surprising reading to exclude artefact feels prudent. In a high cord lesion, though, a sudden surge with flushing points to a dysreflexic crisis that can be life-threatening. Rechecking, or recording an ECG, leaves the noxious trigger running. Look for and relieve bladder distension first.

The cord-injury guideline calls bladder distension the commonest cause and advises checking the urinary tract first; the anaesthesia text says the crisis usually settles once the stimulus is treated, and in awake patients sitting up, loosening clothing and emptying bladder or bowel may suffice.

Sources: Outside our books: Evaluation and Management of Autonomic Dysreflexia and Other Autonomic Dysfunctions: Preventing the Highs and Lows - Management of Blood Pressure, Sweating, and Temperature Dysfunction (2020)Faust

If weakness worsens after edrophonium, the problem is a cholinergic crisis. Too much anticholinesterase paradoxically weakens muscle, so giving more of it deepens the paralysis. Atropine counters only the muscarinic features, such as secretions, bradycardia and small pupils. It does not restore strength. A rising carbon dioxide level, acidaemia and rapid shallow breathing all mean ventilation is failing, and the threshold to intubate in myasthenia is low. So secure the airway and support ventilation first, withhold anticholinesterases, and let strength return as the drug excess clears.

Atropine controls muscarinic not muscle weakness. It is tempting because the edrophonium response points to cholinergic crisis, and atropine is its familiar antidote. But atropine only controls muscarinic effects. It leaves the muscle weakness untouched, so a tiring, hypercapnic patient still needs intubation and ventilation.

A fall in tidal volume after edrophonium indicates cholinergic crisis. Atropine may be needed for the muscarinic symptoms, but weakness worsens and the patient needs intubation. Edrophonium worsens cholinergic crisis. Hypercarbia warns of ventilatory failure, and the threshold for intubation in myasthenia is low.

Sources: Mayo reviewFaustMiller 10e

Anticholinesterase treatment helps myasthenia only up to a point. Doses above that point weaken muscles instead of strengthening them. Edrophonium is itself a short-acting anticholinesterase. If the weakness comes from too little drug (myasthenic crisis), a small intravenous dose of 1–2 mg improves strength. If the weakness comes from too much drug (cholinergic crisis), the same dose adds to the excess, so the weakness gets worse. Muscarinic signs such as salivation, small pupils and a slow heart rate also appear.

Worsening after edrophonium means cholinergic. The patient is known to have myasthenia and is getting weaker, so a myasthenic crisis seems the obvious answer. But a myasthenic crisis gets better after edrophonium. Weakness that gets worse after edrophonium means the patient already has too much anticholinesterase, which is the opposite problem.

Stoelting and Faust both say that too much anticholinesterase can itself cause weakness. Edrophonium makes a cholinergic crisis worse but improves a myasthenic one. Salivation, miosis and bradycardia go with the cholinergic form.

Sources: Stoelting 8eFaust

Anticholinesterases raise junctional acetylcholine. Too little leaves transmission failing (myasthenic crisis); too much floods it and adds muscarinic excess (cholinergic crisis). The label comes from signs and the edrophonium response, not the dose history: strength improves in myasthenic crisis but fails to improve or worsens in cholinergic crisis, with small pupils, saliva and a slow pulse. So a myasthenic still weak while on edrophonium has not responded to it: treat as cholinergic, with atropine for the muscarinic effects, stopping the anticholinesterase and securing ventilation. The test is historical.

Give more neostigmine for weakness. Neostigmine tempts because anticholinesterases are first-line treatment and weakness sounds like under-treatment. But a myasthenic still weak while on edrophonium has not improved with it, so this is not myasthenic crisis: more anticholinesterase deepens the paralysis, and atropine treats the muscarinic excess.

Too much anticholinesterase causes cholinergic crisis and too little causes myasthenic crisis, and their treatments clash. Cholinergic crisis is confirmed by muscarinic signs and worse weakness after edrophonium 1–2 mg. Atropine may treat the muscarinic symptoms, but weakness persists and intubation is needed.

Sources: Mayo reviewStoelting 8eFaustBarash 9e

Guillain–Barré is an immune-mediated attack on peripheral nerve roots. Infection or vaccination often triggers it, so treatment targets the immune process early, while the disease is still evolving. Stoelting takes the cautious view that IVIG or plasma exchange helps some patients without changing overall outcome. Miller's, the more recent text, cites considerable evidence that either is equally effective across subtypes, speeding recovery and improving outcome. Both agree steroids add nothing. The conduct that is safe under either view is early IVIG or plasma exchange, supportive care and no steroids.

Most improve without respiratory involvement. New weakness in a child after a vaccine sounds alarming, and the disease can progress, so a poor outlook feels likely. But most patients stabilise and function often returns fully. With no respiratory involvement this child is at the milder end, and the right step is early immunotherapy.

Miller's finds IVIG and plasma exchange equally effective for every subtype, hastening recovery and improving outcome. Stoelting says they help only some patients, do not alter overall outcome, and steroids are useless. Barash rates immunotherapy within two weeks most effective. Vaccination is a recognised trigger.

Sources: Barash 9eMiller 10eStoelting 8e

The posterior optic nerve sits behind the globe. It has little collateral flow, so hours of disturbed perfusion during prone surgery can leave it ischaemic. This is made worse by blood loss, low pressure and venous congestion. Because the injury is retrobulbar, fundoscopy can look normal at first. This separates it from retinal causes, which show changes in the eye itself. Scoliosis correction carries this risk alongside blood loss and cord injury.

Optic neuropathy more common than retinal. Retinal artery occlusion is tempting: it is painless, usually unilateral and recognised in the prone position. However, it requires direct orbital pressure and is much rarer than posterior optic neuropathy after spine surgery. Loss in one eye does not exclude optic neuropathy.

The textbooks list ischaemic optic neuropathy among the specific anaesthetic concerns in scoliosis correction. They say most visual loss after spine surgery is posterior ischaemic optic neuropathy, with cortical blindness and retinal artery occlusion rarer. The fundus may initially look normal.

Sources: Barash 9eStoelting 8e

The artery of Adamkiewicz arises from the aorta at a variable level and feeds much of the anterior cord. Clamping the aorta above it, or covering it with a stent, cuts off that supply. Aortic disease and old grafts have already reduced collateral flow. Cross-clamping also raises CSF pressure, which lowers cord perfusion pressure. Once the cord depends on these weak collaterals, any later fall in perfusion, such as low blood pressure after surgery, can cause infarction. The paralysis may therefore appear hours or days later.

Delayed paraplegia from postop hypotension not intraop. Low blood pressure really can trigger cord injury, so it looks like the cause. But it is a contributing factor, not the lesion. The injury itself is cord ischaemia, and delayed paraplegia is linked to low pressure after surgery, not during it, in a cord with poor collateral supply.

Spinal cord ischaemia is a feared complication of aortic surgery. It causes paraplegia either straight away or after a delay of 12 hours to 21 days. Delayed cases are associated with postoperative hypotension when collateral flow to the cord is only just adequate.

Sources: Miller 10eStoelting 8e

Blood in the subarachnoid space breaks down, and its haemoglobin products most likely irritate the cerebral arteries. Over days the arteries narrow and regional flow falls, causing ischaemic deficits. This is not immediate. Miller puts the earliest symptoms at day 3, and the AHA guideline places most cases between days 4 and 14, giving a working window of days 3 to 14. Clipping removes the rebleeding threat but not the blood around the vessels, so delayed deficits can follow successful surgery.

Vasospasm after clipping, not rebleeding. Rebleeding is the most feared early complication of SAH, so a new deterioration makes people think of it first. Here, though, the aneurysm has been clipped. After successful surgery, the recognised cause of a new delayed deficit is vasospasm-driven ischaemia, which appears in exactly this post-bleed window.

DCI affects about 30% of patients. Miller reports symptoms from days 3–5, peaking days 5–7; the AHA reports mostly days 4–14. Stoelting attributes delayed deficits after successful surgery to vasospasm; Faust suggests that haemoglobin irritating the arteries is the probable cause.

Sources: Miller 10eOutside our books: 2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association (2023)Stoelting 8eFaust

Carbon dioxide controls the tone of the cerebral arterioles. A high PaCO2 dilates them and flow rises. A low PaCO2 constricts them and flow falls. This happens even when perfusion pressure does not change. Barash names PaCO2 as the most important of the chemical regulators. It describes a linear response between 20 and 80 mmHg, with flow changing by about 1 to 2 mL/100 g/min for each mmHg. The words 'most powerful' come from the Brain Trauma Foundation severe head-injury guideline, which is an outside source and not a textbook.

Carbon dioxide more potent than oxygen. Oxygen is tempting because it is the other arterial blood gas, and a lack of oxygen does dilate cerebral vessels. But that reflex only starts when the tissue is truly hypoxic. Across ordinary values, the sources rank carbon dioxide, not oxygen, as the main regulator.

Barash ranks PaCO2 the most important regulator of flow, linear from 20 to 80 mmHg at about 1–2 mL/100 g/min per mmHg. Miller states CO2 alters flow at constant perfusion pressure. The trauma guideline calls it the most powerful determinant.

Sources: Barash 9eMiller 10eOutside our books: Guidelines for the Management of Severe TBI, Fourth Edition (2017)

Active neurones release metabolic byproducts such as potassium, hydrogen ions and lactate, together with glutamate and nitric oxide. These dilate local vessels, so supply keeps pace with demand. The link also works in reverse. Barbiturates, etomidate and propofol can lower metabolic rate by about 60% at burst suppression, and flow falls with it because the coupling stays intact.

Metabolic demand not pressure autoregulation. This option names cerebral blood flow, so it sounds right. But the relationship between pressure and flow is autoregulation, which keeps flow steady when perfusion pressure changes moderately. Here flow rises because metabolic demand rises. Perfusion pressure plays no part in it.

The textbooks define flow–metabolism coupling as regional blood flow rising in proportion to increased neuronal activity and metabolism. Proposed mediators are local metabolic byproducts, glutamate and nitric oxide. When anaesthetic drugs lower metabolism, flow falls to match.

Sources: Barash 9eMiller 10eFaust

In long-standing hypertension, both the lower and the upper limit of the autoregulatory plateau move to higher perfusion pressures. Below the raised lower limit, flow becomes pressure-passive and ischaemia can follow, at a pressure a normotensive brain would handle. So a higher MAP is needed to keep flow steady. Know the patient's usual pressure before you lower it. Volatile agents work differently: they dilate cerebral vessels and reduce autoregulation in a dose-dependent way. Marked hypoxia also disturbs it. Both weaken the plateau; neither moves it.

Volatiles remove plateau, not shift it. This is tempting because volatile agents clearly change the autoregulation curve. But they act by cerebral vasodilation, which reduces autoregulation and removes it altogether at high MAC. Flow then follows pressure directly. The plateau does not move as a whole to higher pressures.

Chronic hypertension shifts the autoregulation curve rightwards; both limits rise, so a higher MAP is needed to maintain steady cerebral flow. Volatile agents impair autoregulation through vasodilation, abolishing it above 2 MAC. Hypoxia below 50 mm Hg also impairs it.

Sources: Stoelting 8eFaustMayo review

Flow follows metabolic demand. Barash puts children well above adults; outside the textbooks, studies show newborn flow is low, climbs to an early-childhood peak, then settles at adult levels, so any infant sits below older children. Against adults the data split: most newborn measurements fall below the adult norm; an older infant approaches or exceeds it. Hydrocephalus decides the rest: autoregulation holds flow only above its lower perfusion limit, an infant's low arterial pressure leaves little margin, and uncompensated raised pressure therefore cuts flow, as Kety and Schmidt showed.

Infant flow exceeds adult flow. Textbooks teach that paediatric flow exceeds adult flow, so this option feels safe. That figure describes older children at peak demand, not newborns, whose flow is lower. Hydrocephalic pressure then reduces perfusion further, so this infant is not above adults.

Barash puts childhood flow 50% to 70% above the adult 50 mL/min/100 g. Outside the textbooks, Wintermark found 40 at 6 months peaking at 130 at 2–4 years; Altman measured preterm 4.9 to 23, term 9.0 to 73. Raised ICP reduces CBF.

Sources: Barash 9eOutside our books: Cerebral Blood Flow Measurement in Healthy Children and Children Suffering Severe Traumatic Brain Injury—What Do We Know? (2020)Outside our books: Cerebral blood flow requirement for brain viability in newborn infants is lower than in adults (1988)

Brain energy use has two parts: signalling work that powers electrical activity, and a basal share that keeps cells intact even when silent. Anaesthetic drugs cannot reach the basal share; cooling is the only way to cut it, and mild cooling acts mostly on it. Flow is matched to local activity and metabolism, and cooling keeps that match intact. So the reduced neural activity and metabolism are the cause; the lower metabolic rate and lower flow are the measured results.

Depressed metabolism is result not mechanism. It sounds right because cooling does lower metabolic rate and flow follows it. But a lower metabolic rate is the result being explained, not the mechanism. The mechanism is depressed neural activity plus depressed basal cellular metabolism, which together lower demand and so flow.

Miller's states that cooling lowers energy use for electrical function and for basal cellular upkeep, and that only cooling reaches the basal part. Blood flow tracks local activity and metabolism, falling when metabolism is suppressed; Faust adds that cooling lowers both without uncoupling them.

Sources: Miller 10eFaust

Lower metabolic demand pulls flow down through coupling, while volatile agents directly relax cerebral vessels. Below 1 MAC these effects roughly cancel, so flow changes little. At higher doses vasodilation wins, and flow rises while metabolism keeps falling. The Mayo review calls this uncoupling; Barash says coupling is never truly lost, only overridden, with the same net result. Volatile agents also depress sensory-evoked potentials in proportion to dose. This is a monitoring effect and does not change the direction of flow or metabolism.

Volatiles raise flow despite metabolic drop. It is tempting because intravenous hypnotics reduce metabolism and flow together, and depressed evoked potentials suggest the whole brain is being turned down. Volatile agents are different: their direct vasodilation keeps flow up, and flow rises further at higher doses even though metabolism falls.

Volatile agents raise cerebral blood flow and lower metabolic rate, both in proportion to dose. Below 1 MAC, coupling cancels most of the vasodilation. The drop in flow that coupling causes still happens, but direct vasodilation outweighs it. These agents also depress sensory-evoked potentials.

Sources: Mayo reviewBarash 9eStoelting 8e

Propofol and barbiturates such as thiopental sharply depress cerebral metabolic rate. Flow stays coupled to metabolism, so CBF falls with it. Propofol's cerebral profile matches the barbiturates', so neither beats the other. Opioids hardly alter metabolism, so flow changes only slightly, as long as ventilation is controlled. Benzodiazepines at sedative doses have only a minor effect and produce a large fall only at anaesthetic doses. Ketamine raises metabolism and flow, and volatile agents dilate cerebral vessels.

Midazolam weaker than thiopental and propofol. Benzodiazepines appear in lists of IV agents that reduce CBF, so midazolam looks plausible. At sedative doses its effect is minor, and only anaesthetic doses bring a significant fall. It is not a potent cerebral vasoconstrictor the way propofol and thiopental are.

Propofol's effects on flow and metabolism mirror those of barbiturates. Both constrict cerebral vessels strongly, lowering CBF, blood volume and ICP. Opioids and sedative-dose benzodiazepines produce only minor falls. Ketamine, like volatile agents, dilates cerebral vessels.

Sources: Miller 10eMayo reviewStoelting 8e

Propofol, thiopental, etomidate and benzodiazepines at induction doses lower the brain's metabolic rate. Because flow stays coupled to metabolism, flow falls with it. Opioids barely change cerebral metabolism, so flow changes little. One text calls them very little effect, another minor decreases and a third mild vasoconstriction. These fit together once ventilation is added: opioid respiratory depression that lets PaCO2 rise would dilate cerebral vessels, so opioids stay near-neutral only when CO2 is controlled. Ketamine does the opposite and raises both metabolism and flow.

Benzodiazepines at anaesthetic doses reduce flow. It is tempting because sedative doses of benzodiazepines hardly change cerebral metabolism or flow. But at doses that induce anaesthesia, midazolam behaves like the other hypnotics and clearly reduces flow. Opioids stay close to neutral.

The texts agree that hypnotic IV agents lower cerebral flow through coupled falls in metabolism. Opioids have very little or only minor effect, and act as vasoconstrictors only if PaCO2 is not allowed to rise. Ketamine is the exception, raising both flow and metabolism.

Sources: Barash 9eMiller 10eStoelting 8e

Cerebral blood flow normally follows metabolic demand. Barbiturates, propofol and etomidate depress neuronal oxygen consumption, so flow falls with it. Opioids hardly change either. Ketamine works the other way: it raises cerebral oxygen consumption, and flow rises with it. Because autoregulation and carbon dioxide reactivity are largely preserved, the increase in flow is driven by metabolism rather than by a failure of vascular control.

Ketamine unique in raising metabolic rate. Volatile agents are well-known cerebral vasodilators, so people link them with a rise in flow. But their effect on flow comes from dilating the vessels, not from any increase in metabolism. The sources name only ketamine as raising cerebral metabolic rate.

Both standard texts agree that ketamine alone raises cerebral oxygen consumption, with a matching modest rise in flow. Barbiturates, propofol, etomidate and benzodiazepines reduce metabolism, and flow falls in step. Opioids barely change either.

Sources: Barash 9eMiller 10e

Only the thoracolumbar segments have the intermediolateral cell column, so all sympathetic outflow starts there. That is why the system is called thoracolumbar. Some sources extend the column to L3. Each preganglionic axon enters the sympathetic chain and may run up or down it before synapsing. There it contacts many postganglionic neurons at several levels. This divergence spreads one spinal signal over wide areas and strengthens it, so sympathetic discharge acts as a widespread mass response.

Sympathetic divergence not convergence pattern. Convergence sounds like a normal feature of neural wiring, because many inputs onto one cell is common in the central nervous system. But the sympathetic pattern is the reverse: one preganglionic fibre fans out to many postganglionic cells. The sympathetic hallmark is divergence, not convergence.

Anaesthesia textbooks place preganglionic sympathetic cell bodies in the intermediolateral grey columns from T1 to L2, though one text extends this to L3. Each preganglionic fibre synapses with several postganglionic fibres above or below its origin, spreading and amplifying the signal.

Sources: Barash 9eFaust

The two autonomic divisions leave the central nervous system from separate regions. Parasympathetic preganglionic cell bodies lie in the midbrain and medulla and leave with cranial nerves III, VII, IX and X. The rest lie in the intermediolateral grey of the second to fourth sacral segments. Their fibres travel all the way to ganglia beside or within the target organ, so their effects are discrete and local. The thoracic and lumbar cord gives rise to the sympathetic division instead, and its effects are diffuse.

Craniosacral not thoracolumbar parasympathetic. It is the other well-known autonomic outflow and sounds like the natural spinal answer, because most autonomic diagrams show the thoracic and lumbar cord. But thoracolumbar outflow is sympathetic. Parasympathetic fibres come from the brainstem and sacral segments, missing the thoracic and lumbar cord completely.

Parasympathetic preganglionic fibres arise in the midbrain, medulla and sacral cord (craniosacral). Cranial outflow runs in cranial nerves III, VII, IX and X; sacral outflow in the second to fourth sacral nerves. Sympathetic outflow is thoracolumbar.

Sources: FaustBarash 9e

The globe is a nearly closed space, so extra blood in the vascular choroid raises the pressure inside it. Carbon dioxide dilates vessels. Hypercarbia therefore increases choroidal blood volume, and intraocular pressure rises. This is why CO2 pneumoperitoneum with steep head-down tilt raises intraocular pressure: absorbed CO2 engorges the choroid, and the tilt raises central venous pressure, which slows venous outflow from the eye. Hypocapnia works the other way. It constricts choroidal vessels and lowers the pressure.

Hypercarbia raises not lowers pressure. This option names the right variable but reverses the direction. People who remember only that CO2 affects eye pressure may pick it. It fails because lower CO2 constricts choroidal vessels, which reduces blood volume in the globe and lowers intraocular pressure.

Barash explains raised intraocular pressure during steep head-down laparoscopy by two mechanisms: higher central venous pressure from the tilt, and a larger choroidal blood volume caused by hypercarbia. Miller lists hypercarbia with raised intraocular and intracranial pressures as concerns in robotic prostatectomy.

Sources: Barash 9eMiller 10e

After an arterial occlusion, blood flow falls in a gradient. At the centre, flow is too low for cells to survive, and they die within minutes: the core. In the surrounding zone, flow of roughly 10 to 20 mL/100 g/min keeps neurons alive but electrically silent, and they can still recover. Collateral vessels support this zone temporarily. The longer the occlusion lasts, the more of it becomes core. Because the cause is inadequate perfusion, treatment aims to restore flow and oxygen delivery.

Penumbra salvageable; core lost immediately. It is tempting because the penumbra does surround the ischaemic area. But damage that happens immediately describes the core, which is lost within minutes. Penumbral tissue is defined by being salvageable: its death is delayed and depends on time, which is why urgent reperfusion is worthwhile.

The infarct core cannot be recovered after a few minutes. The surrounding penumbra is potentially salvageable and sits in the 10 to 20 mL/100 g/min flow band. Collaterals partly supply it, and it progresses to infarction over time unless the blocked vessel is reopened.

Sources: FaustMiller 10eBarash 9e

Standard tables split stroke risk into two groups. The first holds factors a patient is born with or cannot change: older age, a previous stroke, stroke in a close relative, Black ethnicity, male sex and sickle cell disease. The second can be treated: raised blood pressure, smoking, diabetes, carotid disease, atrial fibrillation, heart failure, high cholesterol, and obesity or inactivity. Hypertension matters most for ischaemic stroke, and treating it long term sharply lowers the chance of a first stroke.

Thalassaemia as a listed fixed risk. Thalassaemia tempts because, like sickle cell disease, it is an inherited haemoglobinopathy, and it is not harmless: intermedia and major are hypercoagulable, with thrombosis and stroke, especially after splenectomy. But the standard stroke table names only sickle cell disease; thalassaemia is a haematology-specific risk, weaker than the listed family history.

The textbook table splits stroke factors into inherited ones, namely age, previous stroke, family history, Black race, male sex and sickle cell disease, and modifiable ones. It calls systemic hypertension the leading risk for ischaemic stroke. Thalassaemia patients clot readily; splenectomy adds risk.

Sources: Stoelting 8eMiller 10e