Multiple Sclerosis

Alternative names:

MS

Definition:

A disorder of the central nervous system (brain and spinal cord) involving decreased nerve function associated with the formation of scars on the covering of nerve cells

Causes, incidence, and risk factors:

Multiple sclerosis (MS) affects approximately 1 out of 1,600 people. Women are affected about 60% of the time. The disorder most commonly begins between 20 to 40 years old. MS is one of the major causes of disability in adults under age 65.

Multiple sclerosis involves repeated episodes of inflammation of nervous tissue in any area of the central nervous system (brain and spinal cord). The location of the inflammation varies from person to person and from episode to episode. The inflammation destroys the covering of the nerve cells in that area (myelin sheath). This leaves multiple areas of scar tissue (sclerosis) along the covering of the nerve cells. Sclerosis slows or blocks the transmission of nerve impulses in that area, resulting in the development of the symptoms of MS.

Symptoms vary because the location and extent of each attack varies. There is usually a stepwise progression of the disorder, with episodes that last days, weeks, or months alternating with times of reduced or no symptoms (remission). Recurrence (relapse) is common.

The exact cause of the inflammation associated with MS is unknown. Geographic studies indicate there may be an environmental factor involved with MS. It has a higher incidence in northern Europe, northern United States, southern Australia, and New Zealand than in other areas of the world. There seems to be a familial tendency toward the disorder, with higher incidence in certain family groups than in the general population. An increase in the number of immune cells in the body of a person with MS indicates that there may be a type of immune response that triggers the disorder. The most frequent theories about the cause of multiple sclerosis include a virus-type organism, an abnormality of the genes responsible for control of the immune system, or a combination of both factors.

Risks include a family history of MS and living in a geographical area with a higher incidence rate for MS.