[Clinical Features of Common Types of Dystonia and Practical Approach for Occupational Dystonia]

Dystonia is a movement disorder characterized by sustained muscle contractions that result in abnormal "patterned" movements and/or postural abnormalities. Based on the accompanying symptoms, dystonia can be classified as isolated (i.e., with dystonia only), combined (i.e., with other movement disorders such as myoclonus), or complex (i.e., with symptoms other than movement disorders such as mental retardation). Moreover, dystonia may affect single or multiple parts of the body and accordingly be classified as focal, segmental, multifocal, hemi, or generalized. The most common type of dystonia is isolated focal dystonia, often accompanied with a specific action (task-specific action). The "task-specificity" uniquely illustrates the nature of dystonia, and this phenomenon is most clearly observed in occupation-related dystonias that include musician's and athlete's dystonia. In this article, we first elucidate the general issues of common focal dystonia (cervical dystonia, blepharospasm, and focal hand dystonia) and then present several educational cases of occupational (task-specific) dystonia with some clinical pearls for practical management.