Combined Short-Pulse and Directional Deep Brain Stimulation of the Thalamic Ventral Intermediate Area for Essential Tremor

Objective: Novel deep brain stimulation (DBS) systems allow directional and short-pulse stimulation to potentially improve symptoms and reduce side effects. The aim of this study was to investigate the effect of short-pulse and directional stimulation, in addition to a combination of both, in the ventral intermediate thalamus (VIM)/posterior subthalamic area (PSA) on tremor and stimulation-induced side effects in patients with essential tremor. Materials and Methods: We recruited 11 patients with essential tremor and VIM/PSA-DBS. Tremor severity (Fahn-Tolosa-Marin), ataxia (International Cooperative Ataxia Rating Scale), and paresthesia (visual analog scale) were assessed with conventional omnidirectional and directional stimulation with pulse width of 60 mu s and 30 mu s.Results: All stimulation conditions reduced tremor. The best directional stimulation with 60 mu s reduced more tremor than did most other stimulation settings. The best directional stimulation, regardless of pulse width, effectively reduced stimulationinduced ataxia compared with the conventional stimulation (ring 60 mu s) or worst directional stimulation with 60 mu s. All new stimulation modes reduced occurrence of paresthesia, but only the best directional stimulation with 30 mu s attenuated paresthesia compared with the conventional stimulation (ring 60 mu s) or worst directional stimulation with 60 mu s. The best directional stimulation with 30 mu s reduced tremor, ataxia, and paresthesia compared with conventional stimulation in most patients. Correlation analyses indicated that more anterior stimulation sites are associated with stronger ataxia reduction with directional 30 mu s than with conventional 60 mu s stimulation.Conclusion: Directional and short-pulse stimulation, and a combination of both, revealed beneficial effects on stimulationinduced adverse effects.