Post-Stroke Depression or Fatigue?

Accessible online at: www.karger. com/journals/ene Fatigue is a common complaint in clinical practice. It is a frequent symptom in patients with depression and other psychiatric disorders, cancer, inflammatory, endocrinologic and rheumatologic diseases. It may also develop without any other antecedent condition than a viral infection, leading to what is generally known as the ‘chronic fatigue syndrome’. In neurology, most studies have been performed in multiple sclerosis, but there are some investigations on fatigue in Parkinson’s disease, postpolio syndrome, immune-mediated polyneuropathies, systemic lupus erythematosus, Lyme disease and amyotrophic lateral sclerosis. Although fatigue is a frequent, often disabling, poststroke sequela, there have been only a few investigations on the subject [1–3]. Furthermore, fatigue was usually addressed just as one symptom of poststroke depression. This is why the study by van der Werf et al. in the present issue of European Neurology is particularly timely. The first issue to resolve is a definition problem. Indeed, although there is a popular knowledge of fatigue, the vagueness which surrounds the concept makes difficult any operational definition. The first and most obvious distinction is between objective and subjective fatigue. Objective fatigue is the observable and measurable decrement in performance occurring with the repetition of a physical or mental task, while subjective fatigue is a feeling of early exhaustion, weariness and aversion to effort. In their paper, van der Werf et al. have chosen the term of ‘experienced fatigue’ to describe this feeling of fatigue, which is indeed most relevant to clinical studies. It can also be useful to distinguish between fatigue which develops in connection with activities requiring a sustained effort (fatigability), and fatigue as a primary state which is closer to a lack of initiative with imbalance between motivation (preserved) and effectiveness (decreased). It is also possible to divide the concept of fatigue into various subtypes, namely ‘physical’ fatigue occurring after muscular exertion, ‘somatic’ fatigue related to disease, ‘mental’ fatigue (for example appearing with cognitively demanding tasks or in the presence of neuropsychological disorders) and ‘psychological’ fatigue (for example associated with lack of interest or poor motivation). These subtypes of fatigue (which are not mutually exclusive) can then be expressed at a behavioral level (objective fatigue) or as a state of feeling (subjective fatigue). The limit between normal and pathological fatigue is not clear. The duration (‘chronicity’) and severity of fatigue, associated disability (interference with daily functioning), other symptoms and the request for a medical consultation are signs which point towards an abnormal situation. Van der Werf et al. found that 51% of their stroke outpatients experienced severe fatigue against only 16% of the controls. This difference was also found by Ingles et al. [1], but with a higher proportion of selfreported fatigue problems (68% vs. 36%). In our own experience, poststroke fatigue is often quantitatively and qualitatively different from premorbid fatigue, which is in agreement with studies on fatigue in Parkinson’s disease [4] and multiple sclerosis [5].