Cauda Equina Syndrome

The collection of nerves at the end of the spinal cord is known as the cauda equina, due to its resemblance to a horse’s tail. The spinal cord ends at the upper portion of the lumbar (lower back) spine. The individual nerve roots at the end of the spinal cord that provide motor and sensory function to the legs and the bladder continue along in the spinal canal. The cauda equina is the continuation of these nerve roots in the lumbar and sacral region. These nerves send and receive messages to and from the lower limbs and pelvic organs.

Cauda equina syndrome (CES) occurs when there is dysfunction of multiple lumbar and sacral nerve roots of the cauda equina.

Causes

CES most commonly results from a massive herniated disc in the lumbar region. A single excessive strain or injury may cause a herniated disc, however, many disc herniations do not necessarily have an identified cause. The size of the disc herniation that results in cauda equina is often much larger than normal; however, if the spinal canal is smaller due to conditions such as arthritis, a smaller disc herniation can produce CES.

Potential Causes of CES

• Spinal lesions and tumors
• Spinal infections or inflammation
• Lumbar spinal stenosis
• Violent injuries to the lower back (gunshots, falls, auto accidents)
• Birth abnormalities
• Spinal arteriovenous malformations (AVMs)
• Spinal hemorrhages (subarachnoid, subdural, epidural)
• Postoperative lumbar spine surgery complications
• Spinal anesthesia

Symptoms and Diagnosis

CES is accompanied by a range of symptoms, the severity of which depend on the degree of compression and the precise nerve roots that are being compressed.

Patients with CES may experience some or all of these “red flag” symptoms.

• Urinary retention: the most common symptom. The patient’s bladder fills with urine, but the patient does not experience the normal sensation or urge to urinate.
• Urinary and/or fecal incontinence. The overfull bladder can result in incontinence of urine. Incontinence of stool can occur due to dysfunction of the anal sphincter.
• “Saddle anethesia” sensory disturbance, which can involve the anus, genitals and buttock region.
• Weakness or paralysis of usually more than one nerve root. The weakness can affect lower extremities.
• Pain in the back and/or legs (also known as sciatica).
• Sexual dysfunction.

If a patient is experiencing any of the “red flag” symptoms above, immediate medical attention is required to evaluate whether these symptoms represent CES.

Testing and Diagnosis

Besides a herniated disc, other conditions with symptoms that can be similar to CES include peripheral nerve disorder, conus medullaris syndrome, spinal cord compression and irritation or compression of the nerves after they exit the spinal column and travel through the pelvis – a condition known as lumbosacral plexopathy.

Tests that May be Helpful in Diagnosing CES

• Patient history and physical exam: Extremely important to assess for cauda equina syndrome.
• Magnetic resonance imaging (MRI): A diagnostic test that produces three-dimensional images of body structures using magnetic fields and computer technology. MRI produces images of the spinal cord, nerve roots and surrounding areas.
• CT Scan: An x-ray of the spinal canal that gives good definition of the bone. If CES is secondary to bone collapse from trauma or cancer, this study can help define that. Visualization of the discs are not as easily seen on CT scan. If no MRI is available, this study can give information helpful to evaluate the anatomy of the region, particularly if done in combination with a myelogram described below.
• Myleogram: An X-ray of the spinal canal following injection of a contrast material into the surrounding cerebrospinal fluid spaces; can show displacement on the spinal cord or spinal nerves due to herniated discs, bone spurs, tumors, etc.

Treatment

Once the diagnosis of CES is made and the etiology established, urgent/emergent surgery is usually the treatment of choice. The goal is to free up the compressed nerve roots and give them the best chance of recovery possible. Left untreated, CES can result in permanent paralysis and incontinence.

Those experiencing any of the red flag symptoms should be evaluated by a neurosurgeon or orthopedic spine surgeon as soon as possible. Prompt surgery is the best treatment for patients with CES. Treating patients within 48 hours after the onset of the syndrome provides a significant advantage in improving sensory and motor deficits as well as urinary and rectal function. Even patients who undergo surgery after the 48-hour ideal time frame may experience improvement.

Although short-term recovery of bladder function may lag behind reversal of lower extremity motor deficits, the function may continue to improve years after surgery. Following surgery, drug therapy coupled with intermittent self-catheterization can help lead to a slow, but steady, recovery of bladder and bowel function.

Coping with CES

Follow-up with the patient’s surgeon occurs a few weeks after surgery to check healing and progress. Many of these patients also require long term follow-up with rehabilitation medicine. Cauda Equina is a relatively rare condition and therefore data on long term outlook is limited.

CES can affect people both physically and emotionally, particularly if it is chronic. People with CES may no longer be able to work, either because of severe pain, socially unacceptable incontinence problems, motor weakness and sensory loss – or a combination of these problems.

Loss of bladder and bowel control can be extremely distressing and have a highly negative impact on social life, work and relationships. Patients with CES may develop frequent urinary infections. Sexual dysfunction can be devastating to the patient and his/her partner and may lead to relationship difficulties and depression.

Severe nerve-type (neurogenic) pain may require prescription pain medication with side effects that may cause further problems. If the pain is chronic, it may become “centralized” and radiate to other areas of the body. Neurogenic pain tends to be worse at night and may interfere with sleep. This type of pain tends to produce a burning feeling that can become constant and unbearable. Sensory loss may range from pins and needles to complete numbness, and may affect the bladder, bowel and genital areas. Weakness is usually in the legs and may contribute to problems walking.

It is essential that people with CES receive emotional support from a network of friends and family members, if possible. It is important to work closely with your physician on medication and pain management. There are several medications prescribed to address pain, bladder and bowel problems. In addition, some patients find that physical therapy and psychological counseling help them cope with CES.

Resources for More Information

• Radiopaedia has images of cauda-equina cases caused by different etiologies.
• Cauda Equina Overview
• AAOS Cauda Equina page