Introduction: Deep brain stimulation of the Vim thalamus (DBS) is an effective treatment for medically refractory essential tremor (ET). However, there is currently no consensus regarding optimization of the parameters required for successful long-term DBS management of tremor. We investigated the suitability of quantitative finger tapping (QFT) to monitor tremor response to DBS parameter changes and to determine the optimal parameters for stimulation of the ventral intermediate (Vim) thalamus in ET patients.
Methods: Response of tremor to unilateral stimulation at 9 frequency/pulse width (PW) combinations was evaluated in 15 ET subjects using QFT and the clinical rating scale (CRS) for tremor. Subjects were blinded to randomly programmed test settings.
Results: Compared to no stimulation, tapping variability was reduced by 37-50% and total CRS score by 22-54% when DBS was activated. Quantitative finger tapping showed reasonable sensitivity to changes in frequency and PW and identified the same ‘optimal’ settings as the CRS postural tremor score in 7/15 subjects.
Conclusions: In ET patients treated with DBS, QFT represents a sensitive, reproducible measure of tremor response to changes in stimulation frequency and PW. The method may be a quick and useful adjunct during DBS programming, especially when postural tremor is a major feature of the disease.
Patient Care: For the clinician, the goals of DBS optimization are three-fold: maximize symptom suppression, minimize side effects of current spread to surrounding tissue, and maximize battery life. QFT is a simple and inexpensive method that can easily be integrated into the outpatient setting. We have shown that QFT regularity may be affected by variation in DBS frequency and pulse duration and thus may provide a valuable adjunct during DBS optimization. This approach may be of particular value for patients in whom optimizing the response of postural tremor is a particular goal of treatment.
Learning Objectives: The effects of deep brain stimulation parameters on tremor control in ET patients.