Fatigue in Parkinson's disease: a short update.

This article provides a short update on fatigue in Parkinson's disease (PD), focusing on measurements, prevalence, associated factors, pathophysiology and treatment. As long as there is no universally accepted definition of fatigue the definition used has to be stated. Different aspects of fatigue, namely physical-, mental- and chronic fatigue will be discussed. The many questionnaires used to assess fatigue measure different aspects of fatigue, making comparisons between studies difficult. Examples of uni- and multidimensional self-report questionnaires are given. In PD patients, the wide range of prevalence of fatigue (37-56%) is largely because of varying definitions of fatigue and populations tested. Without understanding the pathophysiology of subjective fatigue, the development of effective therapies is a challenge.