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Paroxysmal Hypnogenic Dyskinesia

Paroxysmal hypnogenic dyskinesia (PHD) or nocturnal paroxysmal dystonia (NPD) is characterized by attacks of dystonia, chorea, or ballism during non-REM sleep.[68,][69] The frequency may be from five times per year to five times per night. These attacks may be associated with EEG signs of arousal, and the patient usually falls asleep after the attack. The usual duration of the attacks is 30 to 45 seconds but may be longer. Sometimes the patients may have daytime attacks of dyskinesia. PHD may be a heterogeneous condition comprising attacks of different durations and clinical features. Although the longer-lasting attacks may represent a movement disorder, typical short-lasting attacks are more likely to represent a frontal lobe seizure.[70,][71] However, it appears that the great majority of cases of PHD represent frontal lobe epilepsy.[72] Indeed, some patients have PHD attacks preceding tonic-clonic seizures.

Etiology

As already stated, PHD represents a form of …