Multiple sclerosis is one of the most common organic diseases affecting the nervous system. It is important not only because it is frequently encountered but also because it almost invariably affects young people. While rarely fatal in its early stages, it may be progressive and cause long incapacity. Moreover, no treatment is available. (One new genetically-engineered drug, Betaseron, appears to stabilize the condition and initial results suggest that it cuts flare-ups of the illness by about one-third).
The disease is termed 'multiple' because it usually affects many parts of the nervous system, and it is characterized by frequent relapses followed by periods of partial and sometimes complete recovery. It is thus multiple both anatomically and chronologically. The spinal cord is perhaps the most frequently affected; its involvement may cause periods of partial to complete paralysis of the legs, and, at times, of the trunk and arms. With or without this weakness or paralysis, there may be fatigue, difficulty reasoning and thinking, lack of coordination, staggering and tremor, or there may be poor coordination plus tremor of the extremities, sometimes of the body and head. Numbness, tingling, and various sensory changes may also occur. Eye symptoms are also common, with nystagmus, periods of double or blurred vision, and even temporary to permanent blindness in one or both eyes. In advanced cases there may be slurred speech and sometimes difficulty with bladder and bowel control.
The disease is most common in cold, damp climates. In Europe, it is found most frequently in the Scandinavian and low countries, the Baltic region, northern Germany, and the UK. It is rare in the Mediterranean countries. In the USA, incidence is considerably greater in the North than in the South; in total about 300,000 Americans had MS in 1998. The disease usually begins between the ages of 20 and 40; the average age at onset is 30 years for females and 34 years for males. The age at onset tends to be lowest in those areas with the highest incidence.