Case report:

“Emergency operating patient for a below knee amputation. He had previously had the amputation of three toes [four days previously] under a local block, also on the emergency list. Assessed as unfit for general anaesthesia. Arterial line inserted prior to spinal anaesthesia. Senior trainee (ST7) attempted a spinal block with the patient in the standard sitting position but was unable to succeed. We then helped the patient into a left lateral position, used a forced air warmer and a low dose of propofol sedation for patient comfort and I tried to site the spinal at several levels before being successful at a higher level. Clear CSF seen and local anaesthetic injected without resistance. No pain reported by patient at any stage. The block developed as expected. Surgery was successfully completed, and patient went to recovery and then the ward uneventfully.  I was called by the vascular surgeons yesterday afternoon [five days after procedure] to say they suspected a cauda equina syndrome and had done an MRI that was being reviewed. I went to see the patient… patient is incontinent of urine and faeces and can't move either of leg suggesting spinal nerve injury. As part of my duty of candour I explained that this may be a very rare complication of spinal anaesthesia. Patient has since had another MRI scan and review of them by neurosurgery, I understand there is no intervention that patient might benefit from and he has been referred for spinal rehabilitation.”

Commentary:

Cauda equina syndrome has been previously associated with neurotoxicity from drugs such as hyperbaric lidocaine [1].  Its incidence has decreased but still remains a rare complication of spinal anaesthesia.  Conus damage may also present with similar pattern of bowel and bladder dysfunction and may be associated spinal needle insertion in or above the L3/4 interspace [2].

References:

[1] Drasner, K. Lidocaine Spinal Anesthesia: A Vanishing Therapeutic Index? Anesthesiology 1997; 87; 469-472

[2] Reynolds, F. Damage to the Conus Medullaris Following Spinal Anaesthesia. 2001; 56(3): 199-298