Suppression of "rubral" tremor with levodopa.

Lesions of the projection pathways from the dentate to the ventrolateral thalamic nucleus in the environs of the red nucleus produce an intractable "rubral" tremor, which has a frequency of around 4 Hz and is present similarly at rest and through posture and action. Rubral tremor. is thought to be related to the resting tremor of Parkinson's disease, for they are indistinguishable in frequency' and both entail synchronous rhythmical activity in VL thalamus neurones.2 Levodopa has a variable suppressive effect on Parkinsonian resting tremor,3 and the rationale for its action is that it repletes diminished concentrations of dopamine in the striatum thereby restoring its inhibitory influence on the thalamus.4 Because of the similarities between rubral and Parkinsonian tremor we: evaluated levodopa treatment in a patient with a mesencephalic angioma producing intractable tremor, the lesion being so circumscribed that it provided a paradigm of rubral tremor. Previously levodopa has been shown to suppress tremor arising from electrolytic lesions of the dentate and interpositus nuclei in monkeys (Macaca mulatta).5