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.
(See also Overview of Spinal Cord Disorders.)
Cauda equina syndrome is not a spinal cord syndrome. However, it mimics conus medullaris syndrome, causing similar symptoms.
Cauda equina syndrome most commonly results from a herniated disk in the lumbar spine. Other causes include congenital neurologic anomalies (eg, spina bifida), spinal cord infection, spinal epidural abscess, spinal cord tumor, spinal cord trauma, spinal stenosis, arteriovenous malformation, 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
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.
