[Possible mechanisms of chronic fatigue syndrome in multiple sclerosis]

One of frequent presentations of multiple sclerosis (MS) is chronic fatigue that may be determined as a subjective decrease of the physic and/or psychic energy level. Fatigue can be divided into asthenia (fatigue in resting state), pathological fatigability (exhaustion during physical loading) and fatigue concomitant with other symptoms (MS exacerbation). There are central as well as peripheral mechanisms of fatigue formation. Frequent is a combination of fatigue and affective disorders in MS, in particular depression, as well as sleep disturbances (insomnia, restless legs syndrome) that may indicate the common origin of their mechanisms, i.e. reduction of serotoninergic and noradrenergic systems activity. Endocrinal and autoimmune components are considered as important in fatigue syndrome formation, the latter exerting more influence on asthenia than on pathological fatigability. Further investigation into pathogenetic mechanisms of asthenia (fatigue in resting state), pathological fatigability (fatigue in active state) and specification of their differential diagnostic features allow not only to understand the essence of this syndrome but to choose an adequate individualized therapy.