La fatigue dans la dystrophie myotonique de Steinert : revue de la littérature et voies de recherche

RésuméDans la dystrophie myotonique de Steinert, la littérature montre l’importance de la plainte de fatigue, sa spécificité, mais aussi les limites des modèles utilisés à ce jour.ObjectifAffiner la compréhension du symptôme de fatigue subjective.MéthodeAnalyser la fatigue dans d’autres affections médicales, dans lesquelles la fatigue a été étudiée.RésultatsLa fatigue subjective, dans une prochaine étude, sera étudiée comme l’équation de trois différents sous-types de fatigue. Une fatigue « centrale », qui serait en lien avec des dysfonctionnements du système nerveux central et avec des altérations cognitives. Une fatigue que nous appelons « adaptative », qui serait la conséquence des efforts mentaux et physiques nécessaires pour compenser le handicap et l’altération fonctionnelle, selon les ressources psychologiques individuelles. Enfin, une fatigue appelée « secondaire », qui serait en lien avec les troubles psychologiques (dépression et/ou anxiété).

Steinert myotonic dystrophy is one of the most frequent adult hereditary myopathies. Literature on fatigue showed how relevant this trouble could be for a majority of patients; and also how specific fatigue could be in Steinert disease, compared to other neuromuscular pathologies: in myotonic dystrophy, fatigue and somnolence are two distinct phenomena; the link between fatigue and pain is not significant; there is no correlation between perceived physical activity and actual physical activity, neither between actual physical activity nor subjective fatigue. Thus, more than in any other muscular diseases, factors that are not purely physical seem to be involved in fatigue felt by patients with Steinert disease.ObjectivesTo better apprehend factors that may be involved in subjective fatigue in Steinert disease.MethodWe have examined literature about other affections for which fatigue were richly documented. Fatigue in Chronic Fatigue Syndrome, Parkinson's disease, Multiple Sclerosis, Alzheimer's disease, Poliomyelitis and Myasthenia is studied. Physical, mental and subjective fatigues are well known different types of fatigue. However, clinically, it seems inefficient to try to understand those concepts separately, since they are highly intricate.ResultsFrom this literature review, we underlie three possible etiologies of fatigue experienced by subjects with Steinert's pathology. 1) Central nervous system, in some degrees of alteration, could lead to an objective reduction of the cognitive and physical endurance abilities and to an accurate perception of these perturbations, which result in objective and subjective fatigues, which are highly correlated. We call it “central fatigue”. 2) The functional handicap requires, from an individual, abnormal muscular efforts and important sustained attention (to avoid falls, and/or to anticipate any leisure activity), leading to both physical and mental fatigues. These fatigues would be more or less intense, depending on adaptative strategies engaged by the individual (socially active or not), this is why we call it “adaptative fatigue”. 3) Psychological distress and fatigue could coexist, and/or maintain one and each other. Fatigue is one of the depression symptoms. But depressed subjects would have a tendency to “over-underestimate” their actual physical and cognitive limitations, leading to a subjective fatigue complaint, which is not correlated with objective physical or cognitive fatigue anymore. Anxiety, as a “hyper-vigilance state”, would create a state of mental draining, and would exhaust the cognitive abilities, leading to high level of subjective fatigue. We call it “secondary fatigue”.ConclusionOur aim now remains in designing a future research, in which we would methodologically study these three factors of fatigue, in adults with Steinert's myotonic dystrophy.