Pearls: hyperkinetic movement disorders.

Hyperkinetic movement disorders are characterized by an excessive degree of involuntary motor activity and are classified by their clinical phenomenology. The five major categories include tremor, dystonia, chorea and ballismus, tics, and myoclonus. This article presents a series of "pearls" for each category of movements, emphasizing the recognition of common disorders as well as rare, but treatable hyperkinesias. In addition to the major categories, clinical pearls also cover drug-induced movement disorders and psychogenic movement disorders.