Cauda Equina Syndrome

A rare but serious low back disorder

Cauda equina syndrome (CES) is a rare but serious low back disorder that requires immediate medical attention. In the lumbar spine (low back) the spinal cord ends and separates into a bundle of nerves. The bundle looks like a horse’s tail and was therefore called the cauda equina (horse’s tail in Latin) by early anatomists.  This bundle of nerves supplies the legs with signals to control the muscles and provide sensation.
Illustration showing lower spine with Cauda Equina

Bowel and Bladder Sensations and Function

These nerves are also responsible for normal bowel and bladder sensations and function, including muscles that assist defecation and urination. However, when several of these nerves are compressed or injured at once, bowel and bladder function may be disrupted.  Most commonly, this compression occurs all at once from a disc herniation or fracture and is associated with significant pain.  Occasionally, CES is more difficult to diagnose because its symptoms developed more gradually and vary in intensity.  This can occur in patients with spinal infections, tumors, or spinal stenosis from bone spur formation.

cauda equina in the lower back

Symptoms Related to Cauda Equina Syndrome

You should see your doctor or seek medical attention quickly if any of the following symptoms develop:

  • Bowel and/or bladder dysfunction causes incontinence (Neurogenic Bladder Dysfunction).  Incontinence usually means the patient has limited or no voluntary control over bowel movements or urination.
  • Progressive and/or severe loss or altered sensations in the groin, anal area, buttocks, and inner thighs.  This is called saddle anesthesia (the areas that would touch a saddle when horseback riding are numb).  Many patients with cauda equina syndrome will also have more typical “sciatica” with pain or altered sensation in the legs or feet.
  • Symptoms may include pain, numbness, tingling sensations, and/or weakness that radiates into one or both legs. Some symptoms cause stumbling or difficulty getting up from a chair.
  • Sexual dysfunction (eg, a recent, significant change in sexual function)

Potential causes

Cauda equina syndrome may be caused by a herniated disc, lumbar tumor, infection in the low back, or lumbar spinal stenosis. Traumatic injury may also cause or contribute to the development of CES; such as falling, car collision, or penetrating injuries (eg, gunshot, stabbing).

Diagnostic process

The doctor performs an in-depth physical and neurological evaluation. This includes reviewing overall health and performing necessary tests. Other parts of the doctor’s exam may include the following:

  • Assess spinal alignment, stability, range of motion, and possibly endurance.
  • Manual testing of the senses, balance, spatial orientation, sensation, strength, and reflexes.
  • Stand up from a seated position, walk on your heels then toes, walk forward and backward, bend side-to-side, and other movements.
  • Evaluate the anal sphincter muscle for muscle damage that may cause incontinence.
  • One or more imaging tests may be ordered. These tests include x-rays, MRI (magnetic resonance imaging), and CT scans. Sometimes myelography is performed with a CT scan. A myelogram involves injecting dye into the space around the nerves and spinal cord.  X-rays or a CT scan obtained after the day has been injected where show areas where nerve impingement prevents normal flow of the contrast dye.

lateral CT scan shows a herniated disc protruding into the spinal canalThe yellow arrow in the sagittal T2 weighted MRI (above) shows a large disc herniation at L4-L5;  the cause of Cauda Equina Syndrome in a patient.


Treatment involves relieving the pressure on nerves. Unlike pressure on a single nerve (sciatica or radiculopathy), in which nerve inflammation may be treated with oral steroids or corticosteroid spinal injections, patients with a true cauda equina syndrome typically need urgent surgery to help reduce the risks for long-term problems, such as bowel, bladder, and/or sexual dysfunction, and/or paralysis. At the time of surgery, the disc fragment or other compressing material is directly removed.

Updated on: 03/14/19
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