BODY WATCH : Oh, Your Aching Back : Your doctor says you have a herniated disc. Or she suggests an MRI. Or chemonucleolysis. Confused? We offer a few definitions.


Here’s a glossary of terms often associated with back pain, a condition that affects an estimated 75 million Americans.

* Cauda equina syndrome: Compression, usually due to the pressure of a massive herniated disc, on a sheaf of nerve roots from the lower spinal cord that spread out like the tail of a horse, hence cauda equina. Symptoms include weakness of the legs, loss of sensation in the skin over the perineum (called saddle anesthesia) and urine retention or incontinence from loss of function in the sphincter muscle. Usually requires prompt surgery.

* Chemonucleolysis: Injection of a disc-dissolving enzyme, such as chymopapain, into the jelly-like center of a herniated disc.

* CT-myelography: Multiview X-ray enhanced through computers after a contrasting dye has been injected into membranes covering the spinal cord.


* Discectomy: Surgical removal of part of a disc compressing a nerve root. (Called microdiscectomy when microscopic or visually aided surgical techniques are used.)

* Discography: Injection of a water-soluble imaging material directly into the jelly-like nucleus of a disc to assess damage and locate the source of pain.

* Fusion: Surgical fusing of two vertebrae by inserting fragments of the patient’s bone (graft) usually taken from the pelvic bone. Space between the two vertebrae may be bridged with bone or held together with metal, such as rods or screws.

* Herniated or ruptured disc: Extrusion of the central, jelly-like material of a spinal disc through its fibrous outer covering.

* Laminectomy: Surgery to remove all or part of the bony arch of a vertebra to gain access to a ruptured disc or to relieve pressure on nerves from bone spurs.

* Magnetic resonance imaging (MRI): Strong magnetic field and computer create highly detailed images of soft tissues, such as muscles, cartilage, ligaments, tendons and blood vessels. It can show disc degeneration, protrusion and rupture, infection and other spinal disorders.

* Sciatica: Pain radiating down the leg below the knee along the distribution of the sciatic nerve, usually related to mechanical pressure and/or inflammation of nerve roots in the lumbar spine, for example, a herniated disc.

* Spinal stenosis: Narrowing of the spinal canal that may produce a bony constriction of the cauda equina, a sheaf of nerve roots in the lower spinal cord. Generally affects people older than 60. Symptoms include leg pain when walking or standing that is relieved by sitting or flexing the spine, and occasionally weakness of the legs.

* Spondylolisthesis: Overlap of a vertebra on the one below. This often results in back pain and can also cause pinching of the nerves that exit at the site of the slip.


Sources: U.S. Food and Drug Administration, U.S. Department of Health and Human Services, Public Health Service, Agency for Health Care Policy and Research.