Multiple sclerosis (MS) is a chronic, disabling disease of the
central nervous system. The disease causes inflammation,
destruction, and scarring of the nerve sheath (called myelin)
that covers nerve fibers in the brain and spinal cord. There can
also be damage to the underlying nerve itself (called the axon).
As a result, electrical signals are slowed or blocked. There are
several types of MS: - Relapsing-remitting MS—Symptoms suddenly
reappear every few months or years, last for a few weeks or
months, and then go back into remission. Symptoms sometimes
worsen with each occurrence. - Primary progressive MS—Symptoms
gradually worsen after they first appear. Relapses and
remissions usually do not occur. - Secondary progressive
MS—After years of relapses and remissions, symptoms suddenly
begin to progressively worsen. - Progressive relapsing
MS—Symptoms gradually worsen after they first appear. One or
more relapses may also occur. A malfunction of the body's immune
system seems to be the cause of MS, but exactl