Isolated continuous rhythmic lingual myoclonus.

Isolated continuous lingual myoclonus is an exceptional entity, poorly documented and understood. A patient with a nonepileptic continuous rhythmical myoclonus, affecting the anterior portion of the tongue, as an independent involuntary disorder, is reported. Electromyography showed low frequency (2-4 Hz) bursts of genioglossus muscles activity. The EEG, visual, auditory and somatosensory evoked responses were normal. Imaging techniques like CT and MRI failed to reveal any brainstem or cerebellar lesion. Lingual myoclonus showed a very good response to sodium valproate.