Epidemiology of dystonia

Epidemiology is the investigation of the distribution and determinants of a disease or condition in a population. Dystonia is the third most common movement disorder, yet little is known regarding its population distribution and causes. Barriers to good studies include its relative rarity, the lack of disease registries such as exist for cancer, and the widespread belief that a substantial proportion of cases may not seek medical attention or are misdiagnosed. Deficiencies in epidemiologic knowledge limit progress in identifying treatments, prevention, or cures for this disabling disorder. In this chapter, we provide an overview of the epidemiology of dystonia, beginning with a short review of epidemiologic concepts as they apply to dystonia. Subsequent sections review what is known regarding the frequency and distribution of dystonia and its determinants. Because much remains to be done in this area, we conclude by identifying important directions for future work.