MS is a disorder of the brain and spinal cord which results from a scattered loss of myelin, a fatty substance that surrounds the nerve cells. Myelin is considered important for separating nerve pathways from each other, so that impulses can travel from one location in the nervous system to another. MS affects people of all ages, but is most likely to begin between the ages of 20 and 40. MS differs markedly from one patient to another. The great variability of this disorder must be considered in each individual case.
MS tends to take one of four clinical courses.
These individuals generally do not have severe long- term disability. Remission from such flare-ups may be complete or partial. Such individuals sometimes develop a progressive form. A minority of people with MS have a severe, progressive form of the disease from onset, where symptoms generally do not remit, but tend to be progressive from the onset. Research is currently going on to try and identify more precise prognostic indicators of disease activity.