Myoclonic status misdiagnosed as movement disorders in Rett syndrome: a video-polygraphic study.

Myoclonic jerks and myoclonic status (MS) are sometimes difficult to distinguish clinically from movement disorders such as hand stereotypies, tremor, and dystonia in Rett syndrome. We describe a rare and complete video-polygraphic study of a girl with Rett syndrome (MECP2 mutation) and MS misdiagnosed as movement disorders and disclosed after video-polygraphic recordings. Corresponding to closely recurring activity of diffuse spike and polyspikes-wave-type paroxysms, rhythmic and, especially, arrhythmic myoclonias, usually asymmetrical and asynchronous, involving mainly right muscle deltoid and rarely followed by an inhibitory phenomenon, appeared. The MS improved and, most importantly, disappeared after the use of levetiracetam, with an evident antimyoclonic efficacy and a marked improvement of daily life for the patient and her caregivers. The difficulty in differentiating some typical nonepileptic behavioral features and movement disorders of patients with Rett syndrome from seizures was overcome using prolonged video-polygraphic recordings in our case.