Palatal tremor suppressed by mouth opening: clinical and neurophysiological correlations in two patients.

We report clinical and neurophysiological findings in two patients with palatal tremor (PT). In both patients a prompt and persistent suppression of palatal movements and clicking sounds is caused by slight passive or active mouth opening. One patient has a typical essential palatal tremor (EPT) according to current classification criteria. The other one has a PT characterized by involuntary activation of levator veli palatini and genioglossus muscles. Objective clicking sounds were observed late during the course of the disease. A symptomatic aetiology was excluded, suggesting a diagnosis of atypical EPT. Our observations further confirm that unusual features of some cases may not fit current PT classification criteria. These two cases have several features that distinguish them from voluntary PT and from psychogenic PT. We emphasize that clear cut modulating phenomena may be relevant features in both typical and atypical involuntary EPT. We finally focus on the significance of jaw posture in determining PT suppression in our patients.