The history of multiple sclerosis (MS) is a detective story spanning more than a century. Many clues have been pieced together, but only now are answers emerging. To appreciate why the trail to a solution has been so long and hard, it is necessary to understand what we scientists now believe to be true about MS.

Multiple sclerosis is one of the most common diseases of the nervous system, afflicting people of virtually all ages around the world, although it has a special preference for young people, especially women, and for those who grew up in northern latitudes.

We believe MS involves a genetic susceptibility, but it is not directly inherited. It usually causes sudden neurologic symptoms including vision loss, paralysis, numbness, and walking difficulties. The symptoms can be diverse and confusing, often coming and going without any pattern, making it difficult to diagnose, even today.

The symptoms appear because nerves in the brain and spinal cord lose their ability to transmit signals. Myelin, a complex substance that surrounds and insulates nerve fibers, is essential for nerves to conduct electricity and carry out their function. Myelin is destroyed in MS.

In MS, cells and proteins of the body’s immune system, which normally defend the body against infections, leave the blood vessels serving the central nervous system, pour into the brain and spinal cord, and destroy myelin. The specific triggering mechanism that causes an immune system to attack its own myelin remains unknown, although a viral infection on top of an inherited genetic susceptibility is a leading suspect.

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Written by Loren A. Rolak, MD. Reproduced by permission from the National Multiple Sclerosis Society, USA. © NMSS, 2003