Pain and regional anaesthesia10 / 13
Lumbar radicular pain: epidural steroid injection47-year-old woman, 70 kg, with 4 months of left L5 radicular leg pain and back pain
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Know this first
- Exclude specific causes first: cancer, infection, trauma, inflammatory disease, cauda equina.
- Steroid injection helps radicular pain more consistently than axial back pain.
- Particulate steroids can infarct the cord in transforaminal injection; dexamethasone is preferred there.
- Review at 2–3 weeks; repeat once if no response, up to three if partial.
The patient
47-year-old woman, 70 kg, with 4 months of left L5 radicular leg pain and back pain; MRI shows an L4–5 disc protrusion.
No bladder or bowel change, no saddle numbness, no weight loss or fever.
Drugs: naproxen, pregabalin 75 mg twice daily; 8 weeks of physiotherapy without benefit.
Vitals: BP 126/80, HR 74, SpO2 99% on air, RR 14.
The examiner asks
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Consider
What are your considerations?
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- A 47-year-old with left L5 radicular pain matching an L4–5 disc, failing conservative care. Patient
- First I exclude serious causes: cauda equina, cancer, infection, fracture or inflammatory disease. Disease
- Her leg pain matters more than her back pain: radicular pain responds better to injection.
Prepare
How do you decide she is suitable?
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- Her symptoms and signs must match the L4–5 level; many people have painless discs. Disease
- Many disc herniations shrink on their own, so conservative care comes first.
- The injection is one part of her plan, alongside physiotherapy, not the whole plan. After surgery
- I check her anticoagulant status and treat any active infection before the procedure. Patient
Plan
How will you do the injection, and how do you consent her?
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- Fluoroscopy with contrast to confirm the epidural space and exclude vascular uptake. Surgery
- Interlaminar and transforaminal work about equally; a paramedian interlaminar route puts steroid nearer her root.
- Particulate steroid can infarct the cord transforaminally, so there I'd use dexamethasone.
- Interlaminar methylprednisolone 40–80 mg; 40 mg is the lowest effective dose.
- Consent: dural puncture headache, subdural spread, bleeding, infection, nerve injury; all rare. Patient
- Review at 2–3 weeks; repeat once if no response, up to three if partial. After surgery
Crisis
Five minutes after injecting lidocaine and steroid her legs go numb, then her hands weaken; she can only whisper. BP 82/44, HR 48, SpO2 90%. What do you do?
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- A rapidly rising block, from subdural or intrathecal spread, now threatening her breathing. Crisis
- A whisper means the block has reached C3–5 and her diaphragm.
- Call for help; supine, oxygen, bag-mask ventilation, intubate if needed.
- No head-up tilt: it pools blood in her legs and cuts brain flow.
- Atropine 1 mg and ephedrine boluses; adrenaline 0.1–1 mcg/kg early if she worsens.
- Ventilated and monitored until the block recedes, then a full neurological check. After surgery
Fatal mistakes
- Injecting without fluoroscopy and contrast.
- Missing cauda equina syndrome.
- Particulate steroid by the transforaminal route.
- Tilting her head-up to stop the block rising.
Checked against: Low back pain and sciatica in over 16s: assessment and management (recommendations) (2016) · Faust · Barash 9e
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