Adult onset myoclonic Huntington's disease



A patient with adult onset Huntington's disease (HD) and prominent action myoclonus is described. Neither epileptiform activity nor electroencephalography (EEG) correlates of the movements was found. Unlike the case with most (nonmyoclonic) HD patients, centro-parietal components of somatosensory evoked potentials (SEPs) were well defined and a clear V2 response was found. Treatment with valproic acid greatly reduced myoclonus suggesting that the σ-aminobutyric acid (GABA) system might be involved in the pathophysiology of myoclonus in HD.