Object: Accurate placement of the leads is crucial in deep brain stimulation (DBS). To optimize the surgical positioning of the lead, a combination of anatomical targeting on MRI, electrophysiological mapping, and clinical testing is applied during the procedure. Electrophysiological mapping is usually done with microelectrode recording (MER), but the relatively undocumented semimicroelectrode recording (SMER) is a competing alternative. In this study the added value and safety of SMER for optimal lead insertion in the subthalamic nucleus (STN) in a consecutive cohort of patients with Parkinson disease (PD) was assessed.
Methods: Between 2001 and 2010, a consecutive single-center cohort of 46 patients with PD underwent DBS of the STN (85 lead insertions). After exclusion of 11 lead insertions for mostly technical reasons, 74 insertions were included for the assessment. Anatomical target localization was based on either 1.5-T MRI or fused 3-T MRI with CT, with reference to anterior commissure-posterior commissure coordinates. Electrophysiological mapping was performed with SMER. Intraoperative clinical testing was dominant in determining the final lead position. The target error was defined as the absolute distance between the anatomical or electrophysiological target and the final lead position. The effect of SMER on anatomical target error reduction and final target selection was analyzed. Also, the anatomical and electrophysiological target error was judged against the different imaging strategies. For safety evaluation, the adverse events related to all lead insertions were assessed.
Results: The use of SMER significantly reduced the anatomical target error from 1.7 (SD 1.6) mm to 0.8 (SD 1.3) mm (p < 0.0001). In particular, the anatomical target error based on 1.5-T MRI was significantly reduced by SMER, from 2.3 (SD 1.5) mm to 0.1 (SD 0.5) mm (p < 0.001). Anatomical target error reduction based on 3-T MRI fused with CT was not significantly influenced by SMER (p = 0.2), because the 3-T MRI-CT combination already significantly reduced the anatomical target error from 2.3 (SD 1.5) mm to 1.5 (SD 1.5) mm compared with 1.5-T MRI (p = 0.03). No symptomatic intracerebral hemorrhage was reported. Intracerebral infection was encountered in 1 patient following lead insertion.
Conclusions: Semimicroelectrode recording has added value in targeting the STN in DBS for patients with PD based on 1.5-T MRI. The use of SMER does not significantly reduce the anatomical target error in procedures with fused 3-T MRI-CT studies and therefore might be omitted. With the absence of hemorrhagic complications, SMER-guided lead implantation should be considered a safe alternative to MER.