Multiple sclerosis is an acute or chronic, steadily progressive or remittent disease of unknown cause, involving chiefly the white matter of the central nervous system. Spinal cord and brain (including cerebrum, cerebellum and brain stem) are involved, concomitantly or separately. Peripheral nerves (cranial and spinal) and their roots are seldom affected. The cellular gray matter of the brain and spinal cord may infrequently be the seat of lesions, but the clinical features are mainly dependent on extensive involvement of fiber tracts. Inasmuch as the onset, course and degree of dysfunction resulting from the disease are characterized by great variability from one person to the next, though within the framework of a general pattern common to most, and since the cause is unknown, it has been proposed that the illness is not a specific disease entity but a syndrome, perhaps polyetiologic.
The prominent identifying features of the condition are (1) discreteness