Fatigue (a lack of energy) is a common and important manifestation of MS and is even more common than numbness and tingling. Although not specific to MS, it occurs in the vast majority of patients. Many report that it is their major problem. Increased fatigue accompanies most attacks of MS and is an important factor aggravating other manifestations of MS. In actuality, when many patients complain of “fatigue,” they often are referring to fatigability.
A typical example of this occurs when a patient begins walking with-out difficulty, but after a hundred yards or so must either hold onto another person or object or must stop. A large number of patients run out of energy by mid-day and must stop and rest. An unexplained severe lack of energy often precedes other symptoms with the onset of an attack of MS. Most physicians, including neurologists, find it difficult or impossible to assess fatigue.
Therefore, scoring systems for quantifying this complaint have been developed to help evaluate its response to treatment. Some physicians use these “fatigue scales,” but others reject them as being “too subjective.” Fatigue responds to certain drugs, but in contrast, fatigability often requires limitation and pacing of physical activity.
It is important to distinguish these terms because “fatigue,” as defined by social security, is actually fatigability a is a criterion for the evaluation of disability. The proper use of the extended disability scoring system (EDSS) by a neurologist experienced in its use is a valid way of evaluating “fatigue” (fatigability).