Cauda Equina Syndrome Symptoms and Causes

Cauda equina syndrome is a rare condition in which exposed nerve fibers at the bottom of the spinal cord become irritated. The term cauda equina means “horse's tail,” earning the name because of the resemblance.

Under normal conditions, the sensitive nerve tissue that comprises the spinal cord and nerve roots is encased in the spinal canal, within the center of the spinal column, and protected from anomalies that may put pressure on it and cause pain and/or altered functionality. 

Most of the time, cauda equina syndrome is caused by a large, centralized herniated disc between the areas of L4/5 and L5/S1 (these are lower sections of the spine; "L" meaning lumbar and "S" meaning sacral, with the numbers designating individual vertebrae). According to research reviewed by the British Medical Journal, only about 0.12% of all herniated discs in the U.S. cause cauda equina.

Other, less common causes include trauma or injury to the spine that leads to fractures and/or dislocations (subluxations). Tumors or infections that compress the cauda equina may also cause this syndrome. Bone spurs in the spinal canal are another possible cause. Tuberculosis, Pott's paralysis, and iatrogenic causes (examples: spinal manipulation while you're under anesthesia or postoperative complications) are also implicated, as are things may that may occur within spinal spaces, such as cysts.

You may be predisposed to cauda equina syndrome if you have spinal stenosis (congenital or acquired). If acquired stenosis underlies your cauda equina syndrome, most likely the stenosis comes from disc and facet joint degeneration. You may also have a thickened ligamentum flavum (elastic tissue bands that cover the spinal canal) and a narrowing of the spinal canal itself.

Cauda equina syndrome occurs in two basic categories—complete and incomplete—based on the defining symptom: urinary retention, which can include difficulty urinating or a lack of urge to urinate.

Complete cauda equina is accompanied by urinary retention while incomplete is not. With incomplete cauda equina syndrome, you may experience reduced urinary sensation, have a small stream, or similar symptoms, but you're still able to urinate.

Urinary retention can be serious—it's very important to get checked if you notice any changes in this functionality.

Other symptoms of cauda equina syndrome include sexual dysfunction, bowel dysfunction, and/or numbness or other sensory changes around your anus. (Numbness around the anus is called "saddle anesthesia.")

Of course, back pain is also a symptom, as are sensory or motor changes in your lower limbs, such as weakness and/or loss of reflexes.

Cauda equnia syndrome symptoms may present themselves in one of three general “types:” 

• Type 1: Acute symptoms that come on suddenly and intensely. Herniated disc-related causes present this way. 
• Type 2:The final destination after a long journey of chronic back pain, with or without sciatica. 
• Type 3: Insidious progression, where you've slowly been experiencing more and more numbness, as well as urinary symptoms. 

Cauda equina syndrome results from an interruption or dysfunction of the nerves associated with the lumbar and sacral vertebrae. However, such disruption is only diagnosed as cauda equina when your bladder, bowel, and/or sexual function is impaired. This includes saddle numbness/loss of feeling around the anus.

Cauda equina syndrome can be diagnosed with an MRI, x-ray with dye injected into the spinal canal (myelogram), specialized nerve testing such as nerve conduction velocity tests and/or testing electrical activity in muscles (electromyography), and CT scans.

If your doctor suspects you have cauda equina, the physical exam will include palpation (touch) to determine the degree of feeling and response around your anus and rectum.​

Once your cauda equina syndrome diagnosis is confirmed, and if your MRI shows the pressure on the cauda equina to be reversible, surgery may make the most sense. Since many cases of cauda equina syndrome stem from a herniated disc, the procedure of choice will likely be spinal decompression surgery, probably a discectomy.

That said, sometimes emergency surgery is required to avoid permanent dysfunction of your lower extremities, as well as your bladder, bowel, or sexual functioning.

If something other than a herniated disc is creating the pressure on your cauda equina, you'll likely need to work with a specialist to address that problem, as well.

When it comes to cauda equina syndrome, and the areas of the body it affects, it's only natural to feel embarrassed about discussing what you notice, or apprehensive about getting checked. Don't put off treatment. This condition is potentially life-threatening, especially if you ignore symptoms or treat them too late. Speaking with your doctor as soon as you notice symptoms may save your life—or at the very least, your quality of life.