Paroxysmal kinesigenic dyskinesia: a channelopathy? Study of 19 cases

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by brief episodes of dystonia and choreoathetosis triggered by sudden voluntary movements. Disease onset is seen in the first or second decade. The attacks typically last less than one minute. Three autosomal dominant PKD loci are identified: EKD1, EKD2 and EKD3. EKD1 has an overlap with the locus of the "Infantile Convulsion and Choreoathetosis (ICCA) syndrome". The favorable natural history, the episodic nature of the symptoms and their sensitivity to anticonvulsant therapy suggest channelopathy as a mechanism of PKD. We reviewed the clinical features, the family history, the treatment response, the evolution and the technical investigations in 19 affected individuals. All cases were idiopathic. Ten patients had a positive familial history. Three patients suffered from ICCA syndrome. Some atypical features were seen, such as the association of kinesigenic and nonkinesigenic attacks and the presence of migraine, ataxia, seizures and myoclonus. Acetazolamide responsiveness was seen in two patients. The coexistence of PKD and nonkinesigenic dyskinesia in several patients confirms the earlier described presence of intermediary forms, nonrepresented in the current classification of paroxysmal dyskinesias. Our study results suggest channel dysfunction and basal ganglia involvement in the pathophysiology of PKD.