Cauda equina syndrome is a rare condition that is caused by injury to the lumbosacral nerve roots. It has been associated with ultra-fine spinal catheters, especially when hyperbaric lidocaine has been injected, when it is thought to result from poor mixing of local anaesthetic in the cerebrospinal fluid and pooling of anaesthetic in the terminal dural sac, especially if large doses are used to extend an inadequate block. Local anaesthetics are known to be directly neurotoxic in high concentrations, lidocaine more than bupivacaine. The cauda equina nerve fibres may be more vulnerable to damage than other structures because they lack protective sheaths.
Although rare, cauda equina syndrome due to lumbar disc herniation has been reported in the early postpartum period.
Problems and special considerations
Early symptoms may include lower limb neurological deficit and bladder and bowel disturbances. Isolated areas of numbness on the leg and disturbances of perineal sensation are relatively common after delivery, sometimes making diagnosis difficult. Occasionally, obstetric-related neurological deficit may be permanent. Cauda equina syndrome may also be confused with arachnoiditis; for typical features of the two conditions, see Chapter 55, Arachnoiditis.
Management options
Scrupulous attention to technique should be used when performing regional analgesia and anaesthesia. Special precautions should be taken when using continuous spinal blockade (e.g. avoiding lidocaine, especially in high concentrations, and not injecting large volumes of hyperbaric solutions). Once the diagnosis is suspected, early involvement of a neurologist is mandatory, since detailed follow-up and possibly long-term support will be required. There is no specific treatment for cauda equina syndrome (other than urgent decompression in cases of acute traumatic compression), although steroids maybe tried. Psychological support is important, as the consequences of the condition may be catastrophic.
Key points
• Cauda equina syndrome results from damage to the lumbosacral nerve roots; the condition occurs soon after the insult.
• Although rare, it may cause permanent neurological damage.
Further reading
Cook TM, Counsell D, Wildsmith JA; Royal College of Anaesthetists Third National Audit Project. Major complications of central neuraxial block: report on the 3rd National Audit Project of the Royal College of Anaesthetists. Br J Anaesth 2009; 102: 179-90.
Kowe O, Waters JH. Neurologic complications in the patient receiving obstetric anesthesia. Neurol Clin 2012; 30: 823-33.