Paroxysmal hypnogenic dyskinesia responsive to doxylamine: a case report.

Paroxysmal hypnogenic dyskinesia is a rare clinical entity characterized by intermittent dystonia and choreoathetoid movements that begin exclusively during sleep, often with consciousness preserved once the patient is awakened during the episodes. They occur almost every night and are often misdiagnosed as sleeping disorders. Paroxysmal hypnogenic dyskinesia is currently known to be a form of frontal lobe epilepsy, but not in all cases. We present a 19-year-old male patient with paroxysmal hypnogenic dyskinesia who responded to antihistamines. This supports an alternative theory from 1977 (before the cases had been adequately described) that the disorder lies in dysregulation in the basal ganglia. This description now appears similar to acute dystonic reactions such as extrapyramidal symptoms from antipsychotic medications, which also respond to antihistamines.