Deep Brain Stimulation for Orthostatic Tremor: An Observational Study.

Background: Primary orthostatic tremor (OT) can affect patients' life. Treatment of OT with deep brain stimulation (DBS) of the thalamic ventral intermediate nucleus (Vim) is described in a limited number of patients. The Vim and posterior subthalamic area (PSA) can be targeted in a single trajectory, allowing both stimulation of the Vim and/or dentatorubrothalamic tract (DRT). In essential tremor this is currently often used with positive effects.

Objective: To evaluate the efficacy of Vim/DRT-DBS in OT-patients, based on standing time and Quality of Life (QoL), also on the long-term. Furthermore, to relate stimulation of the Vim and DRT, medial lemniscus (ML) and pyramidal tract (PT) to beneficial clinical and side-effects.

Methods: Nine severely affected OT-patients received bilateral Vim/DRT-DBS. Primary outcome measure was standing time; secondary measures included self-reported measures, neurophysiological measures, structural analyses, surgical complications, stimulation-induced side-effects, and QoL up to 56 months. Stimulation of volume of tissue activated (VTA) were related to outcome measures.

Results: Average maximum standing time increased from 41.0 s ± 51.0 s to 109.3 s ± 65.0 s after 18 months, with improvements measured in seven of nine patients. VTA (n = 7) overlapped with the DRT in six patients and with the ML and/or PT in six patients. All patients experienced side-effects and QoL worsened during the first year after surgery, which improved again during long-term follow-up, although remaining below age-related normal values. Most patients reported a positive effect of DBS.

Conclusion: Vim/DRT-DBS improved standing time in patients with severe OT. Observed side-effects are possibly related to stimulation of the ML and PT.