multiple sclerosis

Multiple sclerosis (MS) is a long-lasting disease in which the body's own immune system mistakenly attacks the brain and spinal cord — the central nervous system, which is the headquarters that processes thoughts, senses, and movement. The immune system normally fights off germs, but in MS it turns on a fatty wrapping called myelin that coats the body's nerve fibers. Think of myelin like the plastic insulation around an electrical wire: it lets signals zip along quickly and cleanly. When the immune system strips that insulation away — a process called demyelination — the underlying wire is left bare and damaged, so messages slow down, get garbled, or stop getting through at all.

Because the brain and spinal cord control so much, this damage can show up almost anywhere, and it differs from person to person: blurred or double vision, numbness or tingling, weakness, clumsy balance, deep fatigue, or trouble thinking clearly. The disease earns its name from the scattered patches of hardened scar tissue (called sclerosis, from the Greek for hardening) it leaves behind in many places throughout the nervous system. In its most common early form, symptoms come and go in flare-ups separated by quieter periods of partial or full recovery; over years, however, the bare nerve fibers themselves can wither, and the damage may build into steadily growing, lasting disability.

There is no cure yet, but MS is no longer untreatable. Medicines that calm or redirect the overactive immune system can reduce how often flare-ups strike and slow the long-term decline, while other treatments and rehabilitation help people manage day-to-day symptoms. MS most often begins in young adulthood and affects women more than men, and although its exact trigger is still unknown, scientists believe it grows out of a tangle of genetic susceptibility and environmental factors — including low vitamin D, smoking, and a common virus called Epstein–Barr.