Nocturnal paroxysmal dystonia: a clinical form of focal epilepsy.

Different paroxysmal movements occur during sleep. They correspond either to epileptic seizures of sleep, or to parasomnia. Recently, other nocturnal motor phenomena have been described in the literature as nocturnal or hypnogenic paroxysmal dystonia (NPD), paroxysmal arousal, episodic nocturnal wanderings, etc. The NPD are involuntary nocturnal movements characterized by the association of dystonic postures, tonic movements of the four limbs and the body axis, automatisms, affective mimicry, and vocalization. In certain patients, the EEG records show abnormalities characteristic of epilepsy; in others, the EEG appears normal. A large proportion of the patients present epileptic seizures as antecedents. Typical generalized tonic-clonic seizures can follow an NPD. The NPD are improved with anti-epileptics. The considerable similarity of the clinical and paraclinical signs and of the effects of anti-epileptic treatments do not seem to justify the individualization of different subgroups as a function of the EEG patterns: the NPD are always the result of focal epilepsy, and never of a pathology of movement or of parasomnia. Numerous arguments based on the symptoms and the EEG suggest that these seizures involve the mesial frontal regions.