A potentially disabling, neurodegenerative disease of the brain and spinal cord (central nervous system) wherein the immune system attacks the myelin (protective sheath) covering the nerve fibers and causes communication problems between the brain and the rest of the body.  The disease eventually can cause the nerves themselves to deteriorate or become permanently damaged.  It can cause problems with the optic nerves and vision (including double vision or loss of vision), balance, muscle weakness and control, muscle spasticity, tremor, painful involuntary contractions, trouble with sensation, coordination, dizziness or vertigo, slurred speech, erectile dysfunction, pregnancy problems, numbness, tingling, paralysis, mental and sometimes psychiatric problems.