The disks between the vertebrae are liable to displacement when put under strain. Heavy lifting may produce forces which cause a lumbar intervertebral disk to move out of place ("slipped disk").
Spinal disc herniation is an injury to the cushioning and connective tissue between vertebrae, usually caused by excessive strain or trauma to the spine. It may result in back pain, pain or sensation in different parts of the body, and physical disability. The most conclusive diagnostic tool for disc herniation is MRI, and treatment may range from painkillers to surgery. Protection from disc herniation is best provided by core strength and an awareness of body mechanics including posture.
When a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion to bulge out beyond the damaged outer rings, the disc is said to be herniated.
Disc herniation is frequently associated with age-related degeneration of the outer ring, known as the anulus fibrosus, but is normally triggered by trauma or straining by lifting or twisting. Tears are almost always postero-lateral (on the back of the sides) owing to the presence of the posterior longitudinal ligament in the spinal canal. A tear in the disc ring may result in the release of chemicals causing inflammation, which can result in severe pain even in the absence of nerve root compression.
Disc herniation is normally a further development of a previously existing disc protrusion, in which the outermost layers of the anulus fibrosus are still intact, but can bulge when the disc is under pressure. In contrast to a herniation, none of the central portion escapes beyond the outer layers. Most minor herniations heal within several weeks. Anti-inflammatory treatments for pain associated with disc herniation, protrusion, bulge, or disc tear are generally effective. Severe herniations may not heal of their own accord and may require surgery.
The condition may be referred to as a slipped disc, but this term is not accurate as the spinal discs are firmly attached between the vertebrae and cannot "slip" out of place.
Signs and symptoms
Typically, symptoms are experienced on one side of the body only.
Symptoms of a herniated disc can vary depending on the location of the herniation and the types of soft tissue involved. They can range from little or no pain, if the disc is the only tissue injured, to severe and unrelenting neck pain or low back pain that radiates into regions served by nerve roots which have been irritated or impinged by the herniated material. Often, herniated discs are not diagnosed immediately, as patients present with undefined pains in the thighs, knees, or feet.
Symptoms may include sensory changes such as numbness, tingling, paresthesia, and motor changes such as muscular weakness, paralysis, and affection of reflexes. If the herniated disc is in the lumbar region, the patient may also experience sciatica due to irritation of one of the nerve roots of the sciatic nerve. Unlike a pulsating pain or pain that comes and goes, which can be caused by muscle spasm, pain from a herniated disc is usually continuous or at least continuous in a specific position of the body.
