Unusual position-sensitive jaw tremor responsive to botulinum toxin.

We report on a woman with a focal position-sensitive jaw tremor present with the jaw held slightly open or while drinking from a cup. Electromyography demonstrated a rhythmic 5 Hz alternating tremor involving masseter and digastric muscles with normal reciprocal inhibition. The tremor was markedly reduced with botulinum toxin injections. Copyright (c) 2005 Movement Disorder Society.