H Multiple sclerosis
Definition
Multiple sclerosis (MS) is a demyelinating acquired disease of the CNS characterized by random and multiple sites of demyelination of the corticospinal tract neurons in the brain and spinal cord.
Incidence and prevalence
There seems to be an increased risk of developing MS in persons living in northern temperate zones such as North America, Europe, and southern portions of New Zealand and Australia. The incidence is greater among inner city dwellers and affluent socioeconomic groups. Evidence for a genetic factor is demonstrated by a 12- to 15-fold increase among first-degree relatives. MS is a disease of young adults. It occurs 2 to 2.5 times more frequently in women than in men. The development of symptoms usually occurs in the third to fourth decade of life.
Pathophysiology
Although the exact cause is unknown, evidence suggests that the disease progresses from an immune-mediated attack on myelin with secondary disruption of axons leading to progressive disability.