The bones of the spine are cushioned by small discs. These discs are round and flat with a tough, outer shell (capsule) that surrounds a jelly-like material (nucleus). When discs are healthy, they act as shock absorbers for the spine, keeping the spine flexible. When discs are damaged by injury, normal wear and tear or disease, they may bulge or rupture, forming a herniated disc (sometimes called a slipped or ruptured disc).
Although injury to the outer covering of a disc can cause pain, often a herniated disc by itself does not cause any discomfort. Pain occurs when pressure from the herniated disc is put on the nerve roots or spinal cord. Pain or numbness may occur in the area of the body affected by the nerve. For example, a herniated disc that presses on one of the nerve roots of the large nerve that extends from the lower back down the back of the leg may cause pain and numbness in the leg (a condition called sciatica).
Herniated discs can occur anywhere in the spine, but most occur in the lower back. Most herniated discs heal on their own over time (one to six months). Many people who have a herniated disc are not aware of it because they have no symptoms of leg or back pain.
Herniated discs can occur in people of all ages but they are most common in people between 35 and 45 years old who perform heavy manual labor or drive motor vehicles for long periods of time.
Symptoms vary greatly, depending on the position of the herniated disc. If the herniated disc is:
- Not pressing on a nerve, there may be a low backache or no symptoms at all
- Pressing on a nerve, pain or numbness can occur in the area of the body leading from the nerve
- Located in the neck, pain or numbness may be felt in the shoulders, arms or chest
- Located in the lower back, sciatica may occur and cause leg pain and other nerve-related symptoms, such as weakness, numbness or tingling in one leg. Pain from a herniated disc in the lower back (sciatica) may be felt in the buttock and down the back of the leg to the ankle or foot. There may be low back pain, but it is usually not as severe as leg pain.
Nerve-related symptoms of a herniated disc include:
- Tingling ("pins and needles" sensation) or numbness in one leg that can begin in the buttock or behind the knee and extend to the ankle or foot
- Weakness in certain muscles in one or both legs
- Weakness in both legs and the loss of bladder and/or bowel control, which are symptoms of a specific and severe type of nerve root compression called cauda equina syndrome. This is a serious problem that requires immediate medical help.
Other symptoms of a herniated disc may include severe deep muscle pain and muscle spasms.
Herniated discs are caused by aging, degeneration of the disc (disc disease) or injury to the spine. Disc disease may result from tiny tears or cracks in the outer shell (capsule) of the disc. The jelly-like material inside the disc (nucleus) may be forced out through the tears or cracks in the capsule. This causes the disc to bulge, break open or break into sections.
Disc disease may develop as part of the normal aging process. After age 30, the nucleus of a spinal disc begins to lose its fluid content, becoming less springy and more easily injured.
Injury to the spine can occur from:
- A sudden heavy strain or increased pressure to the lower back. Sometimes a sudden twisting movement or even a sneeze will force some of the jelly-like material inside the disc out through the disc's outer shell.
- Activities that are done over and over again that may stress the lower back, including poor lifting habits, prolonged exposure to vibration or sports-related injuries.
For patients with leg and back pain, the doctor will take a medical history and conduct a physical exam to determine whether symptoms might be caused by a herniated disc.
X-rays are generally not useful. However, if the doctor suspects a more serious underlying condition (such as a tumor, infection or severe nerve damage), or if leg pain and other symptoms do not get better after two to four weeks of nonsurgical treatment, X-rays may be taken. Other tests, such as blood tests, may also be done to rule out other conditions.
A magnetic resonance imaging (MRI) scan may be done to confirm the location and seriousness of a herniated disc or to look for another condition, such as an infection or tumor. An MRI provides detailed images of the soft tissues of the spine, including the muscles, tendons, ligaments and discs. Computed tomography (CT) scans may also be done to provide detailed images of bony structures of the spine.
Electromyography, which can be used to diagnose certain nerve and muscle disorders, may be done for people who have signs of prolonged pressure on a nerve root. However, results of this test will not determine if a herniated disc is causing the nerve root compression.
The goals of treatment are to:
- Relieve pain, weakness or numbness in the leg and lower back
- Prevent further injury by teaching the patient techniques and exercises for care of the back
More than 90% of patients who have a herniated disc will improve within six months after nonsurgical treatment. For this reason, nonsurgical treatment is usually tried before surgery is considered. Nonsurgical treatment usually includes:
- Bed rest, followed by a gradual increase in activity
- Medication to control pain and inflammation
- Exercises recommended by the doctor or physical therapist to help reduce pain and strengthen the muscles that support the back
In some cases, herniated discs heal on their own by a process called resorption. During resorption, the body absorbs parts (fragments or tissue) from a herniated disc that has ruptured.
Surgery is done in only a small number (less than 10%) of people who have herniated discs. Surgery may be considered for people who have progressive nerve damage or severe weakness or numbness or for those whose pain has not been relieved by other methods.