Directional Deep Brain Stimulation of the Thalamic Ventral Intermediate Area for Essential Tremor Increases Therapeutic Window

Abstract

Objectives Deep brain stimulation (DBS) of the posterior subthalamic area (PSA) and the ventral intermediate thalamic nucleus (VIM) is a well‐established therapy for essential tremor (ET), but it is frequently associated with side effects like dysarthria or gait ataxia. Directional DBS (dDBS) may be a way to activate fiber tracts more selectively. Is dDBS for ET superior to omnidirectional DBS (oDBS) regarding therapeutic window and clinically as effective as oDBS? Materials and Methods Ten patients with ET treated with PSA/VIM‐DBS were recruited. Therapeutic window served as primary outcome parameter; clinical efficacy, volume of neuronal activation, and total electrical energy delivered (TEED) served as secondary outcome parameters. Therapeutic window was calculated for all three dDBS directions and for oDBS by determining therapeutic thresholds and side effect thresholds. Clinical efficacy was assessed by comparing the effect of best dDBS and oDBS on tremor and ataxia rating scales, and accelerometry. Volume of neural activation and TEED were also calculated for both paradigms. Results For best dDBS, therapeutic window was wider and therapeutic threshold was lower compared to oDBS. While side effect threshold did not differ, volume of neural activation was larger for dDBS. In terms of clinical efficacy, dDBS was as effective as oDBS. Conclusions dDBS for ET widens therapeutic window due to reduction of therapeutic threshold. Larger volume of neural activation for dDBS at side effect threshold supports the notion of persistent directionality even at higher intensities. dDBS may compensate for slightly misplaced leads and should be considered first line for PSA/VIM‐DBS.

Asleep Surgery May Improve the Therapeutic Window for Deep Brain Stimulation of the Subthalamic Nucleus

“…Given the fact that for the awake group, TW also seemed to be wider for dDBS but without reaching statistical significance, we cannot rule out that our analysis was underpowered due to smaller sample size in the awake group. However, these results are generally consistent with previous studies which showed a superiority of directional compared to omnidirectional stimulation regarding therapeutic window (7,11,26). Earlier reports have already shown dDBS to increase TW by either decreasing TT or increasing SET, but our study is the first to show both decrease of TT and increase of SET at the same time with the same single segment.…”

“…With this new lead design, stimulation is supposed to be delivered more precisely with less effect on adjacent areas (9). Several studies could show that directional deep brain stimulation (dDBS) results in a wider therapeutic window (TW), defined by the stimulation current difference between therapeutic threshold (TT) and side effect threshold (SET), for both subthalamic nucleus (STN)-and VIM-DBS (6,8,10,11).…”

Structure-function relationship of the posterior subthalamic area with directional deep brain stimulation for essential tremor

“…In contrast to our findings, a recent study by Bruno and co-workers found a small but significant difference between omnidirectional and directional stimulation of the VIM and PSA. ( Bruno et al, 2020 ). Therefore, whether PSA stimulation may ultimately benefit from directional current steering would need to be explored in additional studies.…”

Deep-Brain Stimulation for Essential Tremor and Other Tremor Syndromes: A Narrative Review of Current Targets and Clinical Outcomes

“…Current commercial systems typically consist of ring contacts segmented in three sections that can be individually activated, although many other designs have been proposed [69]. Early experience has shown that directional stimulation can increase the therapeutic window while reducing the therapeutic current strength relative to omnidirectional stimulation [70][71][72][73][74]. Whether or not this translates into improved patient outcome remains unclear and might depend on the underlying condition and target.…”