Approximately 250,000 to 350,000 people in the United States are currently diagnosed with multiple sclerosis (MS). This unpredictable condition affects the transmission of nerve impulses in the central nervous system. Simply put, "multiple sclerosis" refers to the buildup of scar tissue in the brain and spinal cord. In a person with this condition, this scarring, or "sclerosis," happens in multiple locations inside the central nervous system.
Symptoms typically first appear when a person is between the ages of 20 and 40. Loss of coordination and muscle control are common symptoms, although the exact symptoms will depend on what parts of the central nervous system are affected. In many cases, people are only mildly affected by the disease and continue to lead their lives much as they did before their diagnosis.
(For more info, click MS. This full-length article describes this condition in greater detail, with a look at what happens during an attack.)