Syndrome de Fatigue Chronique : une entité à part entière ?

RésuméLe syndrome de fatigue chronique est principalement caractérisé par une fatigue persistante et récurrente, majorée par l’exercice physique et mental, associée à des symptômes cognitifs et des douleurs musculo-squelettiques diffuses. Ce syndrome est à l’origine d’un retentissement marqué. Cependant, son existence reste controversée. Le syndrome de fatigue chronique a été longtemps assimilé à un trouble névrotique ou anxio-dépressif. Plusieurs arguments plaident en faveur de cette hypothèse : des symptômes communs (symptômes cognitifs, asthénie, céphalées et troubles du sommeil), mais également les données épidémiologiques, l’existence de pistes génétiques communes, les données de neuro-imagerie, les données immuno-infectieuses, ainsi que la relative efficacité des thérapies cognitivo-comportementales et d’exercices gradués. Cependant, de nombreux éléments semblent distinguer le syndrome de fatigue chronique des troubles anxio-dépressifs et en faire une entité à part entière : d’une part, l’existence de certains symptômes comme les adénopathies douloureuses, les irritations de gorge et la fatigue généralisée pendant 24 heures à la suite d’un exercice physique, et, d’autre part, l’existence d’anomalies neurobiologiques probablement différentes.

BackgroundAlthough a lot of multidisciplinary literature is available about the Chronic Fatigue Syndrome, the existence of the disorder is still questioned. The process leading to the clinical description of Chronic Fatigue Syndrome was slow. Indeed, sporadic Chronic Fatigue Syndrome-like cases were first described in the 19th and 20th centuries. In the 1950s, Myalgic Encephalomyelitis was described after an outbreak of neurological symptoms at the Royal Free Hospital in London. Myalgic Encephalomyelitis was finally renamed “Chronic Fatigue Syndrome” in 1988. The Chronic Fatigue Syndrome was described as a condition mainly characterized by debilitating, persistent or recurrent fatigue over six months and associated with other related symptoms, and inducing a significant distress or impairment in social, occupational or other important areas of functioning. To date, patients prefer the term “Myalgic Encephalomyelitis” because “Chronic Fatigue Syndrome” seems too much stigmatizing.Definition and international classificationsIn 1994, a consensus was reached on a case definition from the United States Center for Disease Control and Prevention. The International Classification of Diseases, tenth revision, classifies the Chronic Fatigue Syndrome in the category “disorders of the nervous system”. The Diagnostic and Statistical Manual, fourth and fifth versions, do not include this disorder in their classification.EpidemiologyAccording to the United States Center for Disease Control and Prevention definition, the prevalence of Chronic Fatigue Syndrome varies from 0.4 % to more than 2 %. The sex ratio for Chronic Fatigue Syndrome is 3/1 with a higher prevalence in women, particularly between 40 and 49 years old. These epidemiological points are consistent with an anxious or depressive nature.Chronic Fatigue Syndrome symptomatology and anxio-depressive symptomatologyAlthough Chronic Fatigue Syndrome and anxio-depressive disorders have common symptoms (cognitive disorders, asthenia, headaches and sleep disorders), others (tender lymph nodes, sore throat, post-exertional malaise, the absence of pathological mood) are not coherent with the spectrum of depression or anxiety disorders.ComorbiditiesThere is a high prevalence of major depressive disorders, bipolar disorders and personality disorders among subjects with Chronic Fatigue Syndrome.PhysiopathologySome results support a genetic predisposition to the Chronic Fatigue Syndrome, polymorphisms of genes involved in the monoaminergic system being implicated. Neuroimaging studies have shown structural and functional changes in the central nervous system of patients with a Chronic Fatigue Syndrome. These changes are compatible with those observed in anxio-depressive disorders. A central nervous system up-regulation of the serotoninergic system and a low circulating cortisol were also reported in Chronic Fatigue Syndromes whereas there is a down-regulation of this system in major depressive disorders. Several microbian microorganisms have been implicated but their pathogenic relationship with the syndrome has not been demonstrated yet. Particularly, the viral implication was recently overturned. Several immune abnormalities, similar at those shown in major depressive disorders, have also been shown in CFS patients but there is no scientific evidence that they have a causal role in Chronic Fatigue Syndromes.Healthcare managementNo pharmacological treatment, in particular no antidepressant drug, has demonstrated a positive benefit/risk ratio in the treatment of CFS. Cognitive behavior therapy and Graded exercise therapy could improve the Chronic Fatigue Syndrome outcome.ConclusionThe Chronic Fatigue Syndrome is still a controversial disorder, which remains an exclusion diagnosis. Despite its common features and comorbidity with anxio-depressive disorders, the CFS seems to be an independent disease. Further studies are needed to elucidate the etiology and find the optimal treatment of this syndrome.