Cauda equina syndrome: a review of clinical progress
From: Chin Med J (Engl). 2009 May 20;122(10):1214-22
The spinal cord terminates at the level of the intervertebral disc between the first and second lumbar vertebrae, forming the conus medullaris, below which is the filum terminale and a bundle of nerve roots constituting the cauda equina. Cauda equina syndrome, a rare neurological disorder, is a combination of signs and symptoms resulting from lesion of the nerves in the cauda equina. Typical manifestations can be associated variably with the disorders characterized by low back pain, unilateral or usually bilateral sciatica, bilateral weakness of the lower extremities, saddle or perianal hypoesthesia or anesthesia, sexual impotence, together with rectal and bladder sphincter dysfunction.
The term “cauda equina” was first described by a French anatomist Lazarius more than four centuries ago. Three centuries later, Mixter and Barr gave the definition of cauda equina syndrome in the English-language literature.
Cauda equina syndrome is rare, both atraumatically as well as traumatically. Males and females are equally affected, and it can occur at any age but primarily in adults. The incidence of cauda equina syndrome is variable, depending on the etiology of the syndrome. The prevalence among the general population has been estimated between 1:100 000 and 1:33 000. The most common cause of cauda equina syndrome is herniation of a lumbar intervertebral disc. It is reported by approximately 1% to 10% of patients with herniated lumbar discs. The prevalence among patients with low back pain is approximately four in 10 000.
Cauda equina syndrome is often misdiagnosed as other disorders for its symptoms mimic those of other conditions. For some less experienced medical workers, it is difficult to discriminate cauda equina syndrome from conus medullaris syndrome, which is characterized by urinary retention and constipation. The presentation of cauda equina syndrome resembles that of conus medullaris syndrome; however, with the exception that symptoms may be asymmetric. Other conditions with similar symptoms to cauda equina syndrome include peripheral neuropathy, lumbosacral plexopathy, low back pain, Guillain-Barr syndrome, lumbar disk disorders, neoplasms of spinal cord, spinal cord infections, spinal cord injuries, and spinal cord compression, etc.
The prognosis for cauda equina syndrome is traditionally considered to be heavily weighted by multiple factors such as etiology, speed of onset, duration of compression, degree of neurological deficit, symptoms and signs, and levels of spinal involvement.
There is much controversy within the literature regarding the urgency of depression and the prognosis. Some researchers claimed no clear correlation between symptom duration before surgery and functional recovery. McCarthy et al performed a retrospective cohort study and found that the symptom duration before operation and the speed of onset do not affect the outcome more than 2 years after surgery. Gleave and Macfarlane retrospectively reviewed 33 cauda equina syndrome cases and found that the duration of bladder paralysis prior to surgery did not influence the outcome. This view was confirmed by a prospective longitudinal inception cohort study of 33 patients performed by Qureshi and Sell. They found a significantly better outcome in patients who were continent of urine at presentation compared with those who were incontinent. The authors concluded that the severity of bladder dysfunction at the time of surgery was the dominant factor in recovery of bladder function. In a review of a case series of 19 patients surgically treated for cauda equina syndrome, Kennedy et al found that no correlation existed between presence of initial motor dysfunction, bilateral sciatica, level of injury as predictors of a poor outcome. The authors emphasized initial urodynamic studies as bladder function assessment in those patients in whom cauda equina syndrome was suspected. Bohlman even reported significant recovery from late surgical decompression performed 11 years following the initial injury.
