CAUDA EQUINA

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Cauda Equina Syndrome Overview

The spinal cord extends from the brain down through the spinal canal inside the vertebral column. Nerves that branch off of the spinal cord (also called nerve roots) are an extension of the spinal cord and are responsible for sending signals to and from the muscles and other structures throughout the body. These signals allow the brain to interpret information from the body including pain, touch, and sense of position. Outgoing signals allow the brain to control actions of the organs and muscle movements.

The spinal cord ends near the first lumbar vertebra in the lower back, forming the conus medullaris. The fibrous extension of the spinal cord is the filum terminale. The bundle of nerve roots below the conus medullaris is named the cauda equina

Compression or inflammation of the nerve roots can cause symptoms of pain, altered reflexes, decreased strength, and decreased sensation. Although these symptoms can become severe, and in some cases disabling, most are self-limiting and respond to conservative care.

An extreme version of nerve compression or inflammation is cauda equina syndrome. Cauda equina syndrome is a serious condition caused by compression of the nerves in the lower portion of the spinal canal (see Multimedia File 2). Cauda equina syndrome is considered a surgical emergency because if left untreated it can lead to permanent loss of bowel and bladder control and paralysis of the legs.

Cauda Equina Syndrome Causes

Cauda equina syndrome is caused by significant narrowing of the spinal canal that compresses the nerve roots below the level of the spinal cord. Numerous causes of cauda equina syndrome have been reported, including traumatic injury, disk herniation, spinal stenosis, spinal tumors (neoplasms), such as metastatic tumors, meningiomas, schwannomas, and ependymomas, inflammatory conditions, infectious conditions, and accidental causes by medical intervention (iatrogenic causes).

Trauma

* Traumatic events leading to fracture or partial dislocation (subluxation) of the low back (lumbar spine) result in compression of the cauda equina.

* A collection of blood surrounding the nerves following trauma (epidural hematoma) in the low back area can lead to compression of the cauda equina.

* Penetrating trauma (gunshot or stab wounds) can cause damage or compression of the cauda equina.

* A rare complication of spinal manipulation is partial dislocation (subluxation) of the low back (lumbar spine) that can cause cauda equina syndrome.

Herniated Disk

* Most disk herniations will improve on their own (are self-limiting) and respond well to conservative treatment, including antiinflammatory medications, physical therapy, and short periods of rest (one to two days).

* Cauda equina syndrome results from a herniated lumbar disk in 1-15% of cases.

* Of lumbar disk herniations, 90% occur either at the vertebral levels L4-L5 or L5-S1.

* Seventy percent of cases of herniated disks leading to cauda equina syndrome occur in people with a history of chronic low back pain, and 30% develop cauda equina syndrome as the first symptom of lumbar disk herniation.

* Males in their 30s and 40s are most prone to cauda equina syndrome caused by disk herniation.

* Most cases of cauda equina syndrome caused by disk herniation involve large particles of disk material that have completely separated from the normal disk and compress the nerves (extruded disk herniations). In most cases, the disk material takes up at least one-third of the canal diameter.

Spinal Stenosis

* Spinal stenosis is any narrowing of the normal front to back distance (diameter) of the spinal canal.

* Narrowing of the spinal canal can be caused by a developmental abnormality or degenerative process.

* The abnormal forward slip of one vertebral body on another is called spondylolisthesis. Severe cases can cause a narrowing of the spinal canal and lead to cauda equina syndrome (see Multimedia File 3).

Tumors (Neoplasms)

* Cauda equina syndrome can be caused by isolated tumors (primary neoplasms) or from tumors that have spread to the spine from other parts of the body (metastatic spinal neoplasms). Metastatic spine tumors are most commonly from the prostate or lung in males and from the lung and breast in females.

* The most common initial symptom of people with cauda equina syndrome caused by a tumor (spinal neoplasm) is severe low back and leg pain.

* Later findings include lower extremity weakness.

* Loss of feeling in the legs (sensory loss) and loss of bowel or bladder control (sphincter dysfunction) are also common.

Inflammatory Conditions

* Long-lasting inflammatory conditions of the spine, including Paget disease and ankylosing spondylitis, can cause a narrowing of the spinal canal and lead to cauda equina syndrome.

Infectious Conditions

* Infections in the spinal canal (spinal epidural abscess) can cause deformity of the nerve roots and spinal column.

* Symptoms generally include severe back pain and rapidly worsening muscle weakness.

Accidental Medical Causes (Iatrogenic Causes)

* Poorly positioned screws placed in the spine can compress and injure nerves and cause cauda equina syndrome.

* Continuous spinal anesthesia has been linked to cases of cauda equina syndrome.

* Lumbar puncture (spinal tap) can cause a collection of blood in the spinal canal (spontaneous spinal epidural hematoma) in patients receiving medication to thin the blood (anticoagulation therapy). This collection of blood can compress the nerves and cause cauda equina syndrome.

Cauda Equina Syndrome Symptoms

Symptoms of cauda equina syndrome include the following:

* Low back pain

* Pain in one leg (unilateral) or both legs (bilateral) that starts in the buttocks and travels down the back of the thighs and legs (sciatica)

* Numbness in the groin or area of contact if sitting on a saddle (perineal or saddle paresthesia)

* Bowel and bladder disturbances

* Lower extremity muscle weakness and loss of sensations

* Reduced or absent lower extremity reflexes

Low back pain can be divided into local and radicular pain.

* Local pain is generally a deep, aching pain resulting from soft tissue and vertebral body irritation.

* Leg pain (radicular pain) is generally a sharp, stabbing pain resulting from compression of the nerve roots. Radicular pain projects along the specific areas controlled by the compressed nerve (known as a dermatomal distribution).

Bladder disturbance (urinary manifestations) related to cauda equina syndrome include the following:

* Inability to urinate (urinary retention)

* Difficulty initiating urination (urinary hesitancy)

* Decreased sensation when urinating (decreased urethral sensation)

* Inability to stop or control urination (incontinence)

Bowel disturbances may include the following:

* Inability to stop or feel a bowel movement (incontinence)

* Constipation

* Loss of anal tone and sensation

When to Seek Medical Care

Cauda equina syndrome is a surgical emergency. Persons should seek immediate medical care or go to the emergency department if they believe they have symptoms of cauda equina syndrome. Some of the early symptoms related to cauda equina syndrome, including low back pain and muscle weakness, are more often caused by simple disk herniation, which does not require urgent attention. However, if you develop severe pain or loss of sensation or bowel or bladder disturbances, you should contact your physician immediately.

Your chances of regaining normal function and having a positive outcome are related to how long you have had symptoms of cauda equina syndrome. Most experts agree that people with cauda equina syndrome should undergo surgery to make more space for the nerves (lumbar decompression) within 48 hours in order to have the best chance for complete recovery.

Exams and Tests

The initial diagnosis of cauda equina syndrome is made based on findings from the individual's history, symptoms, and physical exam. The physical exam includes testing muscle strength of the lower extremities, evaluating sensation to touch and pain, especially around the groin (perineum), checking the lower extremity reflexes, and evaluating rectal tone, sensation, and reflex.

Imaging studies helpful in the diagnosis include plain x-ray films of the lower back to assess for evidence of trauma or severe arthritis (degenerative changes). MRI with and without contrast provides a detailed look at tumors, infection, intervertebral disks, and nerve roots. This study allows the doctor to determine if the nerves are being compressed, to what degree, and by what structures. Findings from these studies help the surgeon plan the appropriate treatment.

Not all people with back pain and/or leg pain and changes in bowel or bladder function have cauda equina syndrome. More common causes of bladder changes are urinary tract infections, which can be identified by a simple urine test, and diabetes, which can be identified with blood tests.

People with symptoms suggesting a possible infection or tumor should be further evaluated with blood and other tests to identify any abnormalities.

Cauda Equina Syndrome Treatment

Self-Care at Home

Cauda equina syndrome is a surgical emergency. Self-care at home is not appropriate for this condition.

Medical Treatment

Medical treatment options are useful in certain persons, depending on the underlying cause of the cauda equina syndrome. Antiinflammatory agents, such as ibuprofen (Advil, Motrin), and corticosteroids, such as methylprednisolone (Solu-Medrol, Depo-Medrol), can be effective in people with inflammatory processes, including ankylosing spondylitis.

People with cauda equina syndrome caused by an infection should receive appropriate antibiotic therapy. People with spinal tumors (neoplasms) should be evaluated for chemotherapy and radiation therapy.

Caution should be used in any medical management of cauda equina syndrome. Any person with cauda equina syndrome with symptoms of groin numbness (saddle anesthesia) and/or weakness or both legs or loss of bowel or bladder control should wait no more than 24 hours before seeking initial medical management. If no relief of symptoms is achieved during this period, immediate surgical decompression is often recommended to minimize the chances of permanent nerve injury.
Medications

People with infections or tumors (infectious or neoplastic causes) causing cauda equina syndrome should receive the appropriate antibiotics or chemotherapy for treatment of the underlying cause.

In most cases, treatment with medications alone is not indicated because of a need for emergent release of the nerve compression (surgical decompression) of the spinal canal.

Surgery

In many cases of cauda equina syndrome, emergency decompression of the spinal canal is the best treatment option. The goal is to relieve pressure on the nerves of the cauda equina by removing the compressing structures and increasing the space available for the nerves in the spinal canal. Traditionally, cauda equina syndrome has been considered a surgical emergency, with surgical decompression considered necessary within 48 hours of the onset of symptoms.

For people with a herniated disk as the cause of cauda equina syndrome, removal of a portion of the bone surrounding the nerves (laminectomy) is performed and the disk material compressing the nerves is removed (discectomy). Many clinical and experimental reports have presented data on the functional outcome based on the timing of surgical decompression. Some investigators have reported no significant differences in the degree of functional recovery as a function of the timing of surgical decompression. Even with these findings, however, most investigators recommend surgical decompression as soon as possible following onset of symptoms to offer the greatest chances of complete neurologic recovery.

Many clinical and experimental studies have investigated patient outcomes in relation to the timing of surgical decompression. Some investigators have reported no significant differences in the degree of functional recovery as a function of the timing of surgical decompression. Even with these findings, however, most investigators recommend surgical decompression as soon as possible following the onset of symptoms to offer the greatest chances of complete neurologic recovery.

Investigators have attempted to identify specific criteria that can aid in predicting the outcome of persons with cauda equina syndrome.

* People with pain in both legs (bilateral sciatica) have less chance or full recovery than persons with single leg pain (unilateral sciatica).

* People with complete groin numbness (perineal anesthesia) are more likely to have permanent paralysis of the bladder.

* The extent of groin numbness (perineal or saddle sensory deficit) is the most important predictor of recovery.


Follow-up

Persons with cauda equina syndrome should have close follow-up with their surgeon to monitor any changes in function. Early surgery gives the patient the best chance for complete recovery from cauda equina syndrome.

Prevention

Prevention of cauda equina syndrome is focused on early diagnosis by identifying the symptoms described above. While low back pain with leg pain and/or weakness is a common complaint that affects many people, cauda equina syndrome is a rare complication. Doctors should be vigilant in identifying these cases. People should be educated on signs and symptoms that could suggest possible cauda equina syndrome, including change in bowel or bladder function and loss of sensation in the groin.