Though rare, cauda equina syndrome is a severe neurological disorder that can lead to incontinence and even permanent paraplegia if left untreated.
The individual nerve roots at the end of the spinal cord, which provide motor and sensory function to the legs and the bladder, continue along in the spinal canal. The cauda equina (Latin for “horse’s tail”) refers to the sac of nerve roots with a common covering before the end of the spinal cord in the lumbar region.
Cauda equina syndrome most commonly results from a massive disc herniation in the lumbar region. A disc herniation occurs when one of the soft flexible discs that functions as an elastic shock absorber between the bones of the spinal column displaces from its normal position. The herniation occurs after the disc begins to break down with aging and can be precipitated by stress or a mechanical problem in the spine. The result is that the softer, center portion of the disc pushes out and causes pressure on the nerve roots in the lumbar spine. Cauda equina syndrome is caused by this compression of the nerve roots.
Cauda equina syndrome is accompanied by a range of symptoms, the severity of which depend on the degree of compression and the precise nerve roots that are being compressed. Symptoms may include severe low back pain, urinary or bowel incontinence, motor weakness or sensory loss in both legs, and saddle anesthesia (unable to feel anything in the body areas that would sit on a saddle).
Cauda equina syndrome is difficult to diagnose. It is rare and its symptoms mimic those of other conditions. Besides a herniated disk, other conditions with similar symptoms to cauda equina syndrome include peripheral nerve disorder, spinal cord compression, and irritation or compression of the nerves after they exit the spinal column and travel through the pelvis, a condition known as lumbosacral plexopathy.
Another difficulty in diagnosing cauda equina syndrome is that its symptoms may vary in intensity and evolve slowly over time. Also, an x-ray will often not be helpful in detecting the cause of the syndrome.
How then is a physician to know to look for cauda equina syndrome?
Physicians need to be aware of certain “red flags” that indicate cauda equina syndrome. Red flags in someone with back pain include saddle anesthesia, recent onset of bladder dysfunction (such as urinary retention or incontinence), bowel incontinence and motor weakness in the lower extremity. The presence of these symptoms warn of cauda equina compression.
Red flags also may be present in a patient’s history. Recent trauma, a history of cancer or a severe infection may predispose a person to cauda equina syndrome. Any of these diseases can involve the discs or the bones of the lumbar spine and result in cauda equina syndrome. Other conditions that may rarely lead to cauda equina syndrome include osteoporotic vertebral fractures and spinal stenosis.
Besides the classic red flag symptoms, physicians suspecting the syndrome look for reflex abnormalities such as the loss or diminution of reflexes, sensory abnormality in the legs, bladder or rectum, and muscle weakness or wasting in the legs.
MRI (magnetic resonance imaging) or myelograms are diagnostic tools valuable in discovering cauda equina syndrome. MRI uses energy from a powerful magnet to produce cross-sectional images of the back. The MRI is especially helpful in detecting damage or disease of soft tissue such as discs. A myelogram is a liquid dye injected into the spinal column. A myelogram can show pressure on the cauda equina from herniated discs and other conditions.
The incidence of cauda equina syndrome is not related to sex or race. It occurs primarily in adults, though trauma-related cauda equina syndrome is not age specific.
Treatment of cauda equina syndrome is necessary to maximize the likelihood of the bladder and bowel function. Treatment may also prevent further weakness in the lower extremities. Left untreated, cauda equina syndrome can result in paraplegia.
Those experiencing any of the red flag syndromes should seriously consider seeing a neurosurgeon, who provides the operative and non-operative management of neurological disorders. Prompt surgery is the best treatment for patients with cauda equina syndrome. Treating patients within 48 hours after the onset of the syndrome provides a significant advantage in improving sensory and motor deficits as well as urinary and rectal function. Even patients who undergo surgery after the 48-hour ideal time frame may experience significant improvement. Although short-term recovery of bladder function may lag behind reversal of lower extremity motor deficits, the function may continue to improve years after surgery. Following surgery, drug therapy coupled with intermittent self-catheterization can help lead to slow but steady recovery of bladder and sphincter function.
Although steroids have proven useful in the treatment of spinal cord injury and some physicians advocate steroids for cauda equina syndrome, no evidence suggests that they are useful in treatment of cauda equina compression. In fact, some physicians point to the potential risks of high-dose steroid use and do not advocate their use to treat cauda equina syndrome.