Familial and acquired paroxysmal dyskinesias. A proposed classification with delineation of clinical features.

On a clinical basis the paroxysmal dyskinesias can be classified into two distinct categories--familial and acquired. The former begins in childhood and the dyskinesia may or may not be induced by sudden movements (kinesigenic or nonkinesigenic forms). In the familial kinesigenic form, the movements are brief, usually occur daily, and respond readily to anticonvulsants. This form has an autosomal dominant or recessive mode of inheritance. In the familial nonkinesigenic form, the movements are of longer duration, occur less frequently, and rarely respond to anticonvulsants. This form has a clear autosomal dominant mode of inheritance. The etiology is obscure. The acquired form of paroxysmal dyskinesia has a later onset and is an expression of an underlying neurological or metabolic disease. Some cases of acquired paroxysmal dyskinesia are manifestations of unusual forms of epilepsy. In these cases the differential diagnosis may be extremely difficult and must be based on EEG findings during an ictal episode.