Oculomotor abnormalities in Dyssynergia cerebellaris myoclonica.

In 1921 Ramsay-Hunt first described the syndrome of dyssynergia cerebellaris myoclonica (DCM), characterized by the clinical triad of action myoclonus, progressive ataxia and epilepsy with cognitive impairment, subsequently also referred to as the "Ramsay-Hunt syndrome". The cause of the symptoms of this rare degenerative syndrome (incidence: 500,000) is the impairment of a regulatory mechanism between nucleus dentatus, nucleus ruber and the bulbar olive. We present two sisters, aged 29 and 30 years, who were investigated for oculomotor abnormalities. The patients were diagnosed as having DCM according to clinical symptomatology, which was confirmed by neurophysiological and radiological findings. In both cases saccadic velocity was markedly reduced, whereas saccadic latency showed a significant increase. In addition, smooth pursuit eye-movements were abnormal and presented reduced gain. These findings suggest that pontine areas and the vestibulocerebellum also seem to be affected in DCM.