Brief Alert
Tremor Arrest with Thalamic Microinjections
Source: Pahapill PA, et al. Tremor arrest with thalamic microinjections of muscimol in patients with essential tremor. Ann Neurology 1999;46:249-252.
The role of interventional therapies for the treatment of movement disorders is rapidly enlarging. In this context, Pahapill and colleagues have reported a pioneering controlled pilot study in six patients with essential tremor. The patients, undergoing stereotactically placed lesions or placement of deep brain stimulators in the ventralis intermedius (Vim) and adjacent thalamic nuclei, received microinjections in the Vim of an inhibitory neurotransmitter (GABA-A) agonist, muscimol. Prior to lesioning and following the characterization of tremor-synchronous cells, microinjections were done in the Vim. The patients were injected with either saline or muscimol, with no effects observed using the saline control. Tremor was suppressed in all patients following the muscimol injection with a relatively long average latency of seven minutes for the full clinical effect to appear. Subsequent tremor suppression lasted an average of nine minutes. Although the microinjection technique has been extensively used in laboratory animals, this study provides the first indication that selective delivery of neurotransmitters to specific anatomical targets may improve the clinician’s therapeutic repertoire.
Beyond the present context, Pahapill et al’s study provides new insights into the potential mechanisms underlying thalamic lesioning and deep brain stimulation (DBS). Pahapill et al emphasize that the results of the inactivation mimic the effects of thalamotomy or DBS and suggest that GABAergic activation may desynchronize local thalamic networks. This demonstration suggests a potentially wide range of future therapeutic interventions such as combining DBS with directed application of pharmacologic agents. —ns (Dr. Nicholas Schiff is Assistant Professor and Attending Neurologist, Weill-Cornell Medical College and New York Hospital.)
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