Overview of Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory, chronic, degenerative disorder that affects nerves in the brain and spinal cord. Myelin, the fatty substance that surrounds and insulates nerves and facilitates the conduction of nerve impulses is the initial target of inflammatory destruction in multiple sclerosis.

MS is characterized by intermittent damage to myelin, called demyelination. Demyelination causes scarring and hardening (sclerosis) of nerve tissue in the spinal cord, brain and optic nerves. Demyelination slows conduction of nerve impulses, which results in weakness, numbness, pain and vision loss.

Because different nerves are affected at different times, MS symptoms often worsen (exacerbate), improve, and develop in different areas of the body. Early symptoms of the disorder may include vision changes (e.g., blurred vision, blind spots), numbness, dizziness and muscle weakness.

MS can progress steadily or cause acute attacks (exacerbations) followed by partial or complete reduction in symptoms (remission). Most patients with the disease have a normal lifespan.

Incidence and Prevalence of Multiple Sclerosis

MS is the most common neurological cause of debilitation in young people. According to the National Institute of Neurological Disorders and Stroke, about 250,000–350,000 people in the United States have been diagnosed with multiple sclerosis. Worldwide, the incidence of MS is approximately 0.1 percent. Northern Europe, the northern United States, southern Australia, and New Zealand have the highest prevalence, with more than 30 cases per 100,000 people.

MS is more common in women and in Caucasians. The average age of onset is between 20 and 40, but the disorder may develop at any age. Children of parents with MS have a higher rate of incidence (30–50 percent).

Publication Review By: Jean-Raphael Schneider, M.D., Stanley J. Swierzewski, III, M.D.

Published: 01 Jan 2000

Last Modified: 18 Jun 2014