Herniated Disk

A herniated disk (also known as a herniated nucleus pulposus or a slipped disk) occurs when all or part of the nucleus pulposus - an intervertebral disk's gelatinous center - extrudes through the disk's weakened or torn outer ring (anulus fibrosus). The resultant pressure on spinal nerve roots or on the spinal cord itself causes back pain and other symptoms of nerve root irritation.

About 90% of herniations affect the lumbar (L) and lumbosacral spine; 8% occur in the cervical (C) spine and 1% to 2% in the thoracic spine. The most common site for herniation is the L4-L5 disk space. Other sites include L5-S1, L2-L3, L3-L4, C6-C7, and C5-C6.

Lumbar herniation usually develops in people ages 20 to 45 and cervical herniation in those age 45 or older. Herniated disks affect more men than women.

Causes

A herniated disk can be caused by any type of intense pressure on the disk by the vertebrae above and below it. This could be caused by lifting a heavy object improperly, by sudden twisting, by a weakening of the disk covering that occurs with age, or by traumatic injury to the back area. Obesity can also put pressure on the disks, and smoking can contribute to degeneration of the disk material. When the soft interior of the disk bulges out, it places pressure on the nearby nerves of the spinal cord.

Signs and Symptoms

The symptoms of a true herniated disc may not include back pain at all. The symptoms of a herniated disc come from pressure on, and irritation of, the nerves. In the thoracic spine area, thiscan include total paralysis of the legs. The symptoms of a herniated disc in the thoracic area usually include:

• Pain that travels around the body and into one or both legs
• Numbness or tingling in areas of one or both legs
• Muscle weakness in certain muscles of one or both legs
• Increased reflexes in one or both legs that can cause spasticity in the legs

Diagnostic tests

X-ray studies of the spine ate essential to show degenerative changes and to rule out other abnormalities. Films may not show a herniated disk because even marked disk prolapse may show up as normal on an X-ray.

Myelography pinpoints the level of the herniation.

Computed tomography scanning shows bone and soft-tissue abnormalities. It can also show spinal canal compression that results from herniation.

Magnetic resonance imaging defines tissues in areas usually obscured by bone on other imaging tests such as those done with X-rays.

Neuromuscular tests can be used to detect sensory and motor loss and leg muscle weakness.

Treatment

Unless neurologic impairment progresses rapidly, initial treatment is conservative, consisting of bed rest (possibly with pelvic traction) for several weeks, supportive devices (such as a brace), heat or ice applications, and exercise. Nonsteroidal anti-inflammatory drugs reduce inflammation and edema at the injury site. Steroidal drugs such as dexamethasone may be prescribed for the same purpose. Muscle relaxants (diazepam or methocarbamol) may help also.

A herniated disk that fails to respond to conservative treatment may require surgery. The most common procedure, laminectomy, involves removing a portion of the lamina and the protruding nucleus pulposus. If laminectomy doesn't alleviate pain and disability, the patient may undergo spinal fusion to stabilize the spine. Laminectomy and spinal fusion may be performed concurrently.

Chemonucleolysis - injection of the enzyme chymopapain into the herniated disk to dissolve the nucleus pulposus - is a possible alternative to a laminectomy. Microdiskectomy can also be used to remove fragments of the nucleus pulposus.

Prevention

• Keep weight under control and lose excess weight, if possible.
• Regular exercise, including exercises that strengthen the abdominal muscles.
• Careful attention to posture when sitting for long periods of time while working or driving.
• Common sense when stooping, bending, lifting or carrying objects - use of the legs for lifting rather than the back is the key.