Genetics of paroxysmal dyskinesias

Paroxysmal dyskinesias (PDs) are a heterogeneous group of disorders characterized by sudden attacks of involuntary movements that are mostly a combination of dystonia, chorea, athetosis, and ballism. They can sometimes be symptomatic, but usually an underlying cerebral lesion is not present. Most PDs have a genetic background and are divided into kinesigenic, nonkinesigenic, and exercise-induced forms. Recently, the first genes have been identified for paroxysmal nonkinesigenic dyskinesia (MR1) and paroxysmal exercise-induced dyskinesia (PED) (SLC2A1). Whereas the function of the MR-1 protein and the pathophysiology are still poorly understood, mutations in SLC2A1 and their functional characterization predict a reduced transport of glucose across the blood-brain barrier as the underlying mechanism of PED. A locus on chromosome 16 has been described for the kinesigenic forms, but the underlying genetic alterations are unknown. This review summarizes clinical symptoms of the PDs, imaging findings, therapeutic options, and the pathophysiologic background.