Sweet spots of standard and directional leads in patients with refractory essential tremor: white matter pathways associated with maximal tremor improvement
OBJECTIVE
In patients with essential tremor (ET) treated with standard deep brain stimulation (sDBS) whose ET had progressed and who no longer received optimal benefit from sDBS, directional deep brain stimulation (dDBS) may provide better tremor control. Current steering may provide better coverage of subcortical structures related to tremor control in patients with ET and significant progression without optimal response to sDBS.
METHODS
This study included 6 patients with ET initially treated with sDBS whose tremor later progressed and who then underwent reimplantation with dDBS to optimize their tremor control. To investigate the differences in the local effects of sDBS and dDBS, the authors generated the volume of tissue activation (VTA) to calculate the sweet spots associated with the best possible tremor control with no side effects. Then, to investigate the anatomical structures associated with maximal tremor control, the white matter pathways of the posterior subthalamic areas (PSAs) were generated and their involvement with the sDBS and dDBS sweet spots was calculated.
RESULTS
Tremor improvement was significantly better with dDBS (68.4%) than with sDBS (48.7%) (p = 0.017). The sDBS sweet spot was located within the ventral intermediate nucleus, whereas the sweet spot of the dDBS was mainly located within the PSA. The sweet spots of both sDBS and dDBS involved a similar portion of the cerebellothalamic pathway. However, the dDBS had greater involvement of the pallidofugal pathways than the sDBS.
CONCLUSIONS
In patients with ET treated with sDBS who later had ET progression, dDBS provided better tremor control, which was related to directionality and a more ventral position. The involvement of both the cerebellothalamic and pallidofugal pathways obtained with dDBS is associated with additional improvement over the sDBS.
ABBREVIATIONS
CbT = cerebellothalamic; CeM = centromedian nucleus; DBS = deep brain stimulation; dDBS = directional DBS; ET = essential tremor; HARDI = high angular resolution diffusion imaging; LPo = lateropolaris; MNI = Montreal Neurological Institute; Pfug = pallidofugal; RN = red nucleus; ROI = region of interest; sDBS = standard DBS; SIFT = spherical-deconvolution informed filtering of tractograms; SN = substantia nigra; STN = subthalamic nucleus; TRS = tremor rating scale; Vim = ventral intermediate nucleus; Vo = ventralis oralis; Voa = Vo anterior; Vop = Vo posterior; VTA = volume of tissue activation; WM = white matter; ZI = zona incerta.Figure from Kim et al. (pp 1601–1609).
© Copyright 1944-2023 American Association of Neurological Surgeons