Protrusion of one of the shock-absorbing pads that lie between the vertebrae of the spine, also known as a “slipped disc”
The shock-absorbing discs between the vertebrae (bones of the spine) consist of a strong, fibrous outer coat and a soft, gelatinous core. A prolapsed disc occurs when the core pushes outwards, distorting the shape of the disc. If the outer coat ruptures, the condition is termed a herniated disc. When a disc prolapses or herniates, the surrounding tissues become inflamed and swollen. Then, together with the disc, the tissues may press on a spinal nerve or the spinal cord, causing pain.
Although discs in the lower back are most often affected, herniation of the discs in the neck and, rarely, the upper back can occur. People between the ages of 25 and 45 are most vulnerable to disc prolapse or herniation. The disorder is slightly more common in men.
With age, the discs begin to dry out. They also become more vulnerable to prolapse or herniation as a result of the normal stresses of daily life and minor injuries. Sometimes, a disc is damaged by bending forwards or a sharp twisting movement, or by lifting a heavy object incorrectly.
Symptoms of a prolapsed or herniated disc may develop gradually over a period of weeks or may appear suddenly. They may include:
Dull pain in the affected area.
Muscle spasm and stiffness around the affected area that makes movement difficult.
If the disc presses on a spinal nerve, you may also have the following symptoms:
Severe pain, tingling, or numbness in a leg (see Sciatica) or, if the neck is affected, in an arm.
Weakness or restricted movement in the leg or arm.
The pain is frequently relieved by rest but may be made worse by sitting, coughing, sneezing, bending, or bowel movements. Impaired bladder or bowel function may indicate pressure on the spinal cord, and you should consult a doctor urgently in such cases.
Diagnosis is usually made from your symptoms and a physical examination. Your doctor may also arrange for you to have an X-ray, to rule out other causes of back pain, and MRI or CT scanning, which can locate the position of the prolapsed or herniated disc accurately.
Although the disc is permanently damaged, the pain usually improves over 6–8 weeks as the swelling subsides. Your doctor will probably suggest ways in which you can modify physical activities to avoid further stress on your back. He or she may also recommend painkillers and refer you for physiotherapy, which can reduce muscle spasms and speed recovery.
Rarely, pain may be relieved with traction, in which the spine is gently stretched with weights to create more space around a nerve and reduce pressure on it. Some people benefit from an epidural injection or a selective nerve root block, in which a local anaesthetic, sometimes used in combination with a corticosteroid drug (see Locally acting corticosteroids), is injected around the compressed nerve to decrease swelling. If the damaged disc is in the neck, a supportive collar may be helpful.
In a few cases, if bladder or bowel function is impaired due to pressure on a nerve or the spinal cord or if there is severe pain or muscle weakness, urgent surgery on the disc may be required (see Microdiscectomy).
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.