Two types of fatigue can be distinguished. A persistent sense of tiredness may prevent the accomplishment of even light tasks. In the other form, the patient generally feels well at rest, but is overcome by a generalized sensation of fatigue, usually after a few minutes of physical activity; this is termed fatigability and often disappears after a short rest. The most common form of fatigability is in the legs, when strength deteriorates after walking for a short distance. Some patients overexert or try to exceed the limits of their ability by walking with canes when they should be using a motorized wheelchair for long distances. Fatigability may also affect the sensory system; for example, visual ability and clarity deteriorate with prolonged reading, but return after a short rest.

Both types of fatigue are common in MS, and both are thought to have both physiologic and psychological components. The physiologic aspects of fatigue, especially the phenomenon of fatigability, may be related to a marginal ability to conduct nerve impulses through plaques and should be distinguished from psychological fatigue. The latter is characterized by listlessness, languor, apathy, and depression and may respond to antidepressant drugs. Fatigue and other symptoms in MS are characteristically worsened by a hot bath, increased body temperature, and hot weather. Fatigue may be the most important aspect of disability in MS and interferes considerably with activities of daily living.

The most important approach to the treatment of fatigue is to teach patients to pace themselves properly. They should not take on excessive physical activity without the ability to rest. Another approach is to avoid even small increases in body temperature by avoiding long periods of vigorous exercise and warm surroundings. Repeated cold baths or showers may help. Air conditioning is important in hot climates.

Several drugs have been reported to help in some, but not all, patients. These include amantadine; about half of patients taking this drug believe it helps maintain energy. Pemoline (Cylert) has been reported to be beneficial in about two-thirds of patients. Antidepressant drugs can be helpful in some cases. A recent trial with 4-aminopyridine (4-AP) suggested that this compound can reduce fatigue and improve strength and balance for a few minutes or hours; it is still under investigation and is not generally available.

Reproduced with kind permission from:
Sibley WA. Therapeutic claims in multiple sclerosis: a guide to treatments; 4th edition. New York: Demos, 1996
A new edition of Therapeutic claims is in press at present and the information reproduced here will be updated as soon as the book is published.