Dorsal subthalamic nucleus targeting in deep brain stimulation: microelectrode recording versus 7-Tesla connectivity

Abstract

Connectivity-derived 7-Tesla MRI segmentation and intraoperative microelectrode recording can both assist subthalamic nucleus targeting for deep brain stimulation in Parkinson's disease. It remains unclear whether deep brain stimulation electrodes placed in the 7-Tesla MRI segmented subdivision with predominant projections to cortical motor areas (hyperdirect pathway) achieve superior motor improvement and whether microelectrode recording can accurately distinguish the motor subdivision. In 25 patients with Parkinson's disease, deep brain stimulation electrodes were evaluated for being inside or outside the predominantly motor-connected subthalamic nucleus (motor-connected subthalamic nucleus or non-motor-connected subthalamic nucleus, respectively) based on 7-Tesla MRI connectivity segmentation. Hemi-body motor improvement (Movement Disorder Society Unified Parkinson's Disease Rating Scale, Part III) and microelectrode recording characteristics of multi- and single-unit activities were compared between groups. Deep brain stimulation electrodes placed in the motor-connected subthalamic nucleus resulted in higher hemi-body motor improvement, compared with electrodes placed in the non-motor-connected subthalamic nucleus (80% versus 52%, P < 0.0001). Multi-unit activity was found slightly higher in the motor-connected subthalamic nucleus versus the non-motor-connected subthalamic nucleus (P < 0.001, receiver operating characteristic 0.63); single-unit activity did not differ between groups. Deep brain stimulation in the connectivity-derived 7-Tesla MRI subthalamic nucleus motor segment produced a superior clinical outcome; however, microelectrode recording did not accurately distinguish this subdivision within the subthalamic nucleus.

Keywords: Parkinson’s disease; connectivity; deep brain stimulation; subthalamic nucleus; targeting.

Graphical Abstract

Figure 1

Connectivity-derived STN segmentation and MER analysis. (A) 7 T T₂ MRI of an example patient showing the STN in coronal and axial planes. d: dorsal, v: ventral, l: left, r: right. (B) 7 T T₂ MRI registered to the diffusion MRI and the connectivity-derived STN segmentation; motor-connected STN (mc-STN, blue) with projections to the cortical motor areas (transparent blue) and non-motor-connected STN (nmc-STN, green) in the same example patient. The black pointer indicates the dorsal STN motor subdivision. Images are aligned to the commissural line. (C) Baseline-corrected power spectrum for mc-STN and nmc-STN. MUA calculated as mean power >300 Hz. The solid line showing mean and the shading showing standard error. (D) Mean MUA at each recording site, aligned to the active location site (grey shading). Mc-STN in blue and nmc-STN in green. The error bars show standard error. Stippled black line: 1-log P-value from ANOVA calculated at each site. The solid black line, which is the same for ANOVA, calculated in a three-site sliding window. The stars denote significant differences after multiple comparison correction. mc, motor-connected; nmc, non-motor-connected; STN, subthalamic nucleus; MER, microelectrode recording; MUA, multi-unit activity. Sample size MUA: total recordings n = 149 (25 patients, 3 recordings per hemisphere covering the active DBS electrode contact site, for 1 patient the most dorsal active contact site was used, which resulted in 2 recordings for that hemisphere); motor-connected STN recordings n = 27; non-motor-connected STN recordings n = 122.