The condition, herniated nucleus pulposus, is a slipped disk along the spinal cord and occurs when all or part of the soft center of a spinal disk is forced through a weakened part of the disk. Most herniation takes place in the lower back (lumbar area) of the spine. Lumbar disk herniation occurs 15 times more often than cervical (neck) disk herniation, and it is one of the most common causes of lower back pain. The cervical disks are affected 8% of the time and the upper-to-mid-back (thoracic) disks only 1 - 2% of the time.
Disk herniation occurs more frequently in middle-aged and older men, especially those involved in strenuous physical activity. Other risk factors include any congenital conditions that affect the size of the lumbar spinal canal.
A quick snapshot of the spine and its construction provides insight into how and why herniation may take place. The bones (vertebrae) of the spinal column run down the back, connecting the skull to the pelvis. These bones protect nerves that come out of the brain and travel down the back and to the entire body. The spinal vertebrae are separated by disks filled with a soft, gelatinous substance, which provide cushioning to the spinal column. These disks may herniate (move out of place) or rupture from trauma or strain.
In some instances nerve roots (large nerves that branch out from the spinal cord) may become compressed, resulting in neurological symptoms, such as sensory or motor changes.
Symptoms of a herniated lumbar disk include: muscle spasm; muscle weakness or atrophy in later stages; pain radiating to the buttocks, legs, and feet; pain made worse with coughing, straining, or laughing, severe low back pain; tingling or numbness in legs or feet.
A physical examination and history of pain may be all that is needed to diagnose a herniated disk. A neurological examination will evaluate muscle reflexes, sensation, and muscle strength. Often, examination of the spine will reveal a decrease in the spinal curvature in the affected area.
The main treatment for a herniated disk is a short period of rest with pain and anti-inflammatory medications, followed by physical therapy. Most people who follow these treatments will recover and return to their normal activities. A small number of people need to have further treatment, which may include steroid injections or surgery.
It may take several months to a year or more to resume all activities without pain or strain to the back. People with certain occupations that involve heavy lifting or back strain may find it necessary to change job activities to avoid recurrent back injury.