Spinal Cord Injury After Neuraxial Anaesthesia

Spinal cord injury after neuraxial anaesthesia is direct needle trauma, ischaemia, haematoma, infection or chemical injury to the cord. It presents with new sensory, motor or sphincter loss that does not resolve with the block.

Epidemiology. Permanent neurological injury is about 1 in 25,000 to 1 in 100,000 neuraxial blocks. Causes include haematoma, abscess, direct trauma, cord ischaemia (anterior spinal artery syndrome from prolonged hypotension, epinephrine and vasospasm), neurotoxic injection of wrong solution, and pre-existing disease.

Risk factors. Spinal stenosis, pre-existing neurological disease, coagulopathy, hypotension, high spinal level (higher than L2 in adults), cord level needle placement, paraesthesia on injection, intrathecal injection of wrong drug and exposure to disinfectant.

Pathophysiology.

Needle trauma disrupts the cord (conus medullaris ends at L1 to L2). Compression, ischaemia or chemical toxicity cause neuronal death.

Severe pain on needle insertion or injection, persistent paraesthesia, new focal weakness, sensory level, sphincter dysfunction, loss of pain and temperature sense with preserved vibration (anterior spinal syndrome), and flaccid then spastic paralysis.

Red flags.

• Pain or paraesthesia on injection.
• Block that persists beyond expected time.
• New bladder or bowel dysfunction.

Emergency MRI of the spine to exclude compressive causes (haematoma, abscess), and to show cord oedema, syrinx or infarct. Coagulation screen and inflammatory markers. Neurophysiology (nerve conduction and electromyography) after 2 to 3 weeks helps localise the injury.

Differential diagnosis.

• Epidural haematoma.
• Epidural abscess.
• Cauda equina syndrome.
• Transient neurological symptoms.
• Pre-existing myelopathy.
• Anterior spinal artery infarct.

Treat compression surgically within hours. Correct hypotension and maintain mean arterial pressure at 85 mmHg or more for 5 to 7 days in cord injury.

• Noradrenaline: 0.05 to 0.5 microgram/kg/min IV, titrated to mean arterial pressure 85 mmHg or more; maximum 1 microgram/kg/min; monitor arterial pressure and peripheries; central line preferred.
• Methylprednisolone has no proven benefit and is not advised.

Provide rehabilitation, bladder and bowel care, pressure area care and thromboprophylaxis (enoxaparin 40 mg subcutaneously once daily, started once bleeding is excluded; reduce to 20 mg daily if creatinine clearance is under 30 mL/min).

Prevention. Avoid needle placement at or higher than L2, stop at paraesthesia or severe pain, avoid injecting against resistance and use correct labelled solutions.

Monitoring. Neurological examination every 1 to 2 hours initially, bladder scans and pressure areas.

Referral and escalation. Neurosurgery, spinal injury unit and neurology. Disclosure, documentation and incident reporting.