- Overview of Spinal Cord Disorders
- Acute Transverse Myelitis
- Cauda Equina Syndrome
- Cervical Spondylosis and Spondylotic Cervical Myelopathy
- Hereditary Spastic Paraplegia
- Spinal Cord Arteriovenous Malformations (AVMs)
- Spinal Cord Autonomic Dysreflexia
- Spinal Cord Compression
- Spinal Cord Infarction
- Spinal Epidural Abscess
- Spinal Subdural or Epidural Hematoma
- Subacute Combined Degeneration
- Syrinx of the Spinal Cord or Brain Stem
- HTLV-1–Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP)
Cauda equina syndrome occurs when 2 or more of the 18 nerve roots caudal to the conus medullaris 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 disc 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 (rarely), 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 bilateral leg weakness in muscles supplied by L3 through S1 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, spinal radiographs 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 (1).
If cauda equina syndrome is causing sphincter dysfunction (eg, causing urine retention or incontinence) and/or lower extremity weakness, immediate surgery (eg, discectomy, 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.
Treatment reference
1. Kuris EO, McDonald CL, Palumbo MA, Daniels AH. Evaluation and Management of Cauda Equina Syndrome. Am J Med. 2021;134(12):1483-1489. doi:10.1016/j.amjmed.2021.07.021
Key Points
The most common cause of cauda equina syndrome is a herniated disc.
If cauda equina syndrome is possible, immediately do MRI, or if it is not available, do CT myelography.
Patients with symptoms of cauda equina syndrome (eg, lower extremity weakness as well as urinary retention, frequency, or incontinence) require immediate surgical decompression.
