CORTICAL MYOCLONUS IN HUNTINGTONS-DISEASE

We describe three patients with Huntington's disease, from two familie s, in whom myoclonus was the predominant clinical feature. The diagnos is was confirmed at autopsy in two cases and by DNA analysis in all th ree. These patients all presented before the age of 30 years and were the offspring of affected fathers. Neurophysiological studies document ed generalised and multifocal action myoclonus of cortical origin that was strikingly stimulus sensitive, without enlargement of the cortica l somatosensory evoked potential. The myoclonus improved with piraceta m therapy in one patient and a combination of sodium valproate and clo nazepam in the other two. Cortical reflex myoclonus is a rare but disa bling component of the complex movement disorder of Huntington's disea se, which may lead to substantial diagnostic difficulties.