The cause of MS is unknown, but the most attractive theory is that it is an immune reaction to the nervous system. Its symptoms include muscular weakness, loss of coordination, and difficulty with speech and vision. It occurs chiefly in young adults and, like arthritis, can have a very variable course.
Some people have only a single attack.
Others have only a few attacks in a lifetime, recover from these, and experience no disability except during attacks. Others have frequent attacks from which they don't recover completely, but which cause only partial disability. Still others have a slow progression of disability over a period of 10 to 25 years, which eventually leaves them helpless. When attacks occur, symptoms may come and go suddenly and may even vary from hour to hour. MS's extreme variability makes it a perfect disease for quacks.