Fatigue in neuroimmunological diseases

Fatigue is a widespread symptom in numerous neuroimmunological diseases like multiple sclerosis (MS), myasthenia gravis, morbus Behcet, neurosarcoidosis, neuroborreliosis or immune vasculitis. This phenomenon is best investigated in MS. The complex mechanisms underlying fatigue in MS are still poorly understood; alterations in immune system activation, central nervous system dysregulation, impaired nerve conduction, and neuroendocrine dysregulation have to be considered. These immune and neural mechanisms may cause the initial symptoms of fatigue; however, the fatigue symptom may be exacerbated by secondary overlapping factors (e. g. depressive mood, sleep disturbances, unhealthy life style) which are likely associated with the feeling of fatigue. Wessely conceptualised four components of fatigue: behaviour (effects of fatigue), feeling (subjective experience), mechanisms, and context (e. g. environment, attitudes). So far most examinations have dealt with the first or the second component of the multidimensional construct fatigue, either concentrating on the behavioural aspect in the physical or in the cognitive sphere or on the subjective aspect. The Rostock Fatigue Study investigated two of the components: objective performance and subjective fatigue estimation in the cognitive and in the physical sphere. MS patients showed a reversed relationship between below-average objective performance in the cognitive and in the physical sphere and high subjective feeling of tiredness when compared to healthy individuals. The clinical management of fatigue should include an assessment of the various factors that can cause fatigue as well as a step-wise treatment approach that encompasses nonpharmacological approaches and pharmacological interventions.