ABSTRACT
The dystonias have been classified by a variety of criteria, including age at onset, anatomic distribution, etiology, and, most recently, genetics. One of the most striking and puzzling features of certain types of dystonia has been the selective involvement of certain motor programs where dystonic muscle contractions are restricted to specific tasks or motor acts while the same muscles can be activated normally with most or all other activities. Writer’s cramp is the most common and prominent example of the task-specific dystonias, but selective hand dystonia can also affect a variety of other manual skills such as typing, sorting, and painting; playing string or keyboard instruments; or engaging in sports like tennis, golf, or snooker. The common theme to all taskspecific dystonias is that they selectively affect highly overlearned and automated types of movement and that treatment often fails to restore the premorbid level of function for the tasks involved. This chapter reviews the clinical features, pathophysiology, prognosis, and treatment of the task-specific dystonias as well as other limb-selective dystonias.
