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Cauda Equina Syndrome


Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Last full review/revision May 2021| Content last modified May 2021
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Cauda equina syndrome occurs when the nerve roots at the caudal end of the cord are compressed or damaged, disrupting motor and sensory pathways to the lower extremities and bladder.

Cauda equina syndrome most commonly results from a herniated disk Herniated Nucleus Pulposus Herniated nucleus pulposus is prolapse of an intervertebral disk through a tear in the surrounding annulus fibrosus. The tear causes pain due to irritation of sensory nerves in the disk, and... read more Herniated Nucleus Pulposus  in the lumbar spine. Other causes include congenital neurologic anomalies (eg, spina bifida Spina Bifida Spina bifida is defective closure of the vertebral column. Although the cause is not known, low folate levels during pregnancy increase risk. Some children are asymptomatic, and others have... read more ), spinal cord infection, spinal epidural abscess, spinal cord tumor Spinal Cord Tumors Spinal cord tumors may develop within the spinal cord parenchyma, directly destroying tissue, or outside the cord parenchyma, often compressing the cord or nerve roots. Symptoms can include... read more , spinal cord trauma Cauda equina injury Trauma to the spine may cause injuries involving the spinal cord, vertebrae, or both. Occasionally, the spinal nerves are affected. The anatomy of the spinal column is reviewed elsewhere. Spinal... read more Cauda equina injury spinal stenosis Lumbar Spinal Stenosis Lumbar spinal stenosis is narrowing of the lumbar spinal canal compresses the nerve rootlets and nerve roots in the cauda equina before their exit from the foramina. It causes positional back... read more Lumbar Spinal Stenosis , arteriovenous malformation Spinal Cord Arteriovenous Malformations (AVMs) Arteriovenous malformations (AVMs) in or around the spinal cord can cause cord compression, ischemia, parenchymal hemorrhage, subarachnoid hemorrhage, or a combination. Symptoms may include... read more , and complications after spinal surgery. Many of these conditions cause swelling, which contributes to compression of the nerves.

Symptoms and Signs of Cauda Equina Syndrome

Cauda equina syndrome (like conus medullaris syndrome) causes distal leg paresis and sensory loss in the distribution of the affected nerve roots (often in the saddle area), as well as bladder, bowel, and pudendal dysfunction (eg, urinary retention, urinary frequency, urinary or fecal incontinence, erectile dysfunction, loss of rectal tone, abnormal bulbocavernosus and anal wink reflexes). Urinary retention or incontinence results from loss of sphincter function.

In cauda equina syndrome (unlike in subacute or chronic spinal cord injury), muscle tone and deep tendon reflexes are decreased in the legs. However, if an acute spinal cord injury is severe, muscle tone and deep tendon reflexes are initially decreased or absent (spinal shock), making distinguishing it from cauda equina syndrome difficult soon after injury.

Without treatment, cauda equina syndrome can cause complete paralysis of the lower extremities.

Diagnosis of Cauda Equina Syndrome

  • MRI or CT myelography

If symptoms suggest cauda equina syndrome, MRI should be done immediately if available. If MRI is unavailable, CT myelography should be done.

If traumatic bone abnormalities (eg, fracture, dislocation, subluxation) that require immediate spinal immobilization are suspected and advanced imaging is not immediately available, plain spinal x-rays can be done. However, CT detects bone abnormalities better.

Treatment of Cauda Equina Syndrome

  • Surgery

  • Usually corticosteroids

Usually, treatment focuses on the disorder causing cauda equina syndrome, usually by relieving compression.

If cauda equina syndrome is causing sphincter dysfunction (eg, causing urine retention or incontinence), immediate surgery (eg, diskectomy, laminectomy) is required.

Analgesics should be used as needed to relieve pain. If symptoms are not relieved with nonopioid analgesics, corticosteroids can be given systemically or as an epidural injection; however, analgesia tends to be modest and temporary. Corticosteroids can also reduce swelling.

Key Points

  • The most common cause of cauda equina syndrome is a herniated disk.

  • If cauda equina syndrome is possible, immediately do MRI, or if it is not available, do CT myelography.

  • Surgically evaluate patients with symptoms of cauda equina syndrome (eg, urinary retention, frequency, or incontinence) immediately.

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