Cauda Equina Syndrome
A cauda equina syndrome results from pathological processes affecting the spinal roots below the termination of the spinal cord around L1/L2, hence it is a syndrome of multiple radiculopathies.
Depending on precisely which roots are affected, this may produce symmetrical or asymmetrical sensory impairment in the buttocks (saddle anesthesia; sacral anesthesia) and the backs of the thighs, radicular pain, and lower motor neurone type weakness of the foot and/or toes (even a flail foot). Weakness of hip flexion (L1) does not occur, and this may be useful in differentiating a cauda equina syndrome from a conus lesion which may otherwise produce similar features. Sphincters may also be involved, resulting in incontinence, or, in the case of large central disc herniation at L4/L5 or L5/S1, acute urinary retention.
Causes of a cauda equina syndrome include:
- Central disc herniation
- Tumor: primary (ependymoma, meningioma. Schwannoma), metastasis
- Lumbosacral fracture
- Inflammatory disease, e.g., sarcoidosis (rare)
- Ankylosing spondylitis (rare).
The syndrome needs to be considered in any patient with acute (or acute-on-chronic) low back pain, radiation of pain to the legs, altered perineal sensation, and altered bladder function. Missed diagnosis of acute lumbar disc herniation may be costly, from the point of view of both clinical outcome and resultant litigation.
Ahn UM, Ahn NU, Buchowski JM, Garrett ES, Sieber AN, Kostiuk JP. Cauda equina syndrome secondary to lumbar disc herniation: a metaanalysis of surgical outcomes. Spine 2000; 25: 1515-1522 Markham DE. Cauda equina syndrome: diagnosis, delay and litigation risk. Journal of the Medical Defence Union 2004; 20(1): 12-15