Transient Neurological Symptoms After Spinal Anaesthesia

Transient neurological symptoms (TNS) are back pain radiating to the buttocks and thighs after spinal anaesthesia, without sensory or motor deficit. They begin within 24 hours of the block and resolve within days.

Epidemiology. Incidence is about 14% to 37% with hyperbaric 5% lidocaine, about 0.3% to 1% with bupivacaine, and lower with prilocaine, mepivacaine and chloroprocaine. It is more frequent in lithotomy position and ambulatory knee arthroscopy.

Risk factors. Lidocaine, lithotomy and knee arthroscopy positions, ambulatory surgery, obesity, and male sex.

Pathophysiology.

The mechanism is uncertain. Neurotoxicity of lidocaine to nerve roots, stretch or position related irritation and sacral pooling of anaesthetic are proposed.

Pain in the lower back, buttocks and posterior thighs (sometimes lower legs), described as aching or burning, appearing 2 to 24 hours after recovery from the block, with normal neurological examination, no fever or bladder symptoms. Pain lasts 1 to 7 days (median 2 to 3 days).

Red flags.

• Any motor weakness or sensory loss.
• Sphincter dysfunction.
• Fever or severe back pain.
• Pain lasting over 7 days.

Clinical, after exclusion of other causes by a complete neurological examination. MRI is needed if there is weakness, sphincter disturbance, fever, or symptoms beyond 1 week.

Differential diagnosis.

• Epidural haematoma.
• Epidural abscess.
• Cauda equina syndrome.
• Musculoskeletal pain.
• Disc herniation.
• Meningitis.

Reassure the patient. Treat with anti-inflammatory drugs and opioid analgesia if needed. Heat to the lumbar region and rest are used.

• Ibuprofen: 400 mg orally every 8 hours with food for 3 to 5 days; maximum 1.2 g daily; monitor renal function and blood pressure; avoid in peptic ulcer and renal impairment.
• Diclofenac: 50 mg orally every 8 hours for 5 days; maximum 150 mg daily; avoid in cardiovascular disease, peptic ulcer and renal impairment.
• Paracetamol: 1 g orally every 6 hours; maximum 4 g daily; reduce in hepatic impairment or under 50 kg.
• Tramadol or oxycodone for severe pain: oxycodone 5 mg orally every 4 to 6 hours for up to 3 days; maximum 40 mg daily in opioid naive adults; monitor sedation and respiratory rate; reduce in older adults and hepatic or renal impairment.

Muscle relaxants have no clear benefit.

Prevention. Avoid hyperbaric 5% lidocaine for spinal anaesthesia; choose bupivacaine, prilocaine or chloroprocaine for short procedures.

Monitoring. Telephone review at 24 to 72 hours after ambulatory surgery, with instructions to return for red flags.

Referral and escalation. Urgent imaging and neurosurgical review for any deficit.