Investigation of an unusual, high-frequency jaw tremor with coherence analysis.

Normal physiological tremor of the jaw has a frequency of 6 to 8 Hz. A patient is described with jaw tremor at frequencies of 12 Hz during jaw movement and 15 Hz when the jaw was relaxed. The 15 Hz tremor was driven by synchronous, bilateral bursts of activity in the temporalis and masseter muscles, which alternated with digastric bursts. Coherence analysis indicated the tremor was highly correlated with both opening and closing muscle activity, and that the opening and closing muscles were about 180 degrees out of phase. The existence of two tremors with different, nonphysiological peak frequencies and the influence of attention, relaxation, and movement in switching from one tremor frequency to the other, suggest that more than one generator may be operating.
(2007 Movement Disorder Society)