A Controlled Comparison of Two DBS Targets for Upper Extremity Action Tremor

Action tremor of the arms can be an invalidizing symptom of diseases such as Essential Tremor, Dystonic Tremor, Parkinson's disease and Multiple Sclerosis. In this study we compare the efficacy and safety of two different brain targets for deep brain stimulation (DBS) that both are known to reduce action tremor of the arms. These two targets are called the VIM nucleus of the thalamus (VIM) and the posterior subthalamic area (PSA), which includes the Zona Incerta. Both targets can be reached by one lead (wirh four electrode contact). Patients that are found eligible for DBS because of severe action tremor of the arms are invited to participate. After randomization, half of them are stimulated first in the VIM for 3 months and then in the PSA for 3 months, and the other half first in the PSA and then VIM for 3 months each. Tremor severity is scored on a clinical quantitative scale at baseline and at the end of each of these two 3-month periods, and eventual side-effects are registered. The best target is then selected and after another 6 months scoring is repeated. We intend to provide robust data about whether one of the two targets is superior to the other both regarding ability to reduce tremor efficiently and to avoid or minimize side-effects, or if there is no significant difference between the two targets. We also carefully check the exact position of the active electrode contact in the brain and compare this with efficacy and safety evaluations. Long-term follow-up is planned after 3, 5, 7 and 10 years.