The main feature of the disease is multifocal (disseminated) injury of the central nervous system. The injury causes various neurological symptoms and signs that go on and off (relapsing-remitting form) or progress steadily, and with time cause irreversible damage of the nervous system and permanent disability. In neuropsychological studies, 40-65% of MS subjects show cognitive impairment with prominent involvement of memory, sustained attention and information processing speed. Multiple sclerosis subjects with different disease courses have different cognitive profiles.