Accuracy of Microelectrode Trajectory Adjustments during DBS Assessed by Intraoperative CT

Abstract

Background/aims: Microelectrode recording (MER)-guided deep brain stimulation (DBS) aims to place the DBS lead in the optimal electrophysiological target. When single-track MER or test stimulation yields suboptimal results, trajectory adjustments are made. The accuracy of these trajectory adjustments is unknown. Intraoperative computed tomography can visualize the microelectrode (ME) and verify ME adjustments. We aimed to determine the accuracy of ME movements in patients undergoing MER-guided DBS.

Methods: Coordinates following three methods of adjustment were compared: (1) those within the default "+" configuration of the ME holder; (2) those involving rotation of the default "+" to the "x" configuration; and (3) those involving head stage adjustments. Radial error and absolute differences between coordinates were determined.

Results: 87 ME movements in 59 patients were analyzed. Median (IQR) radial error was 0.59 (0.64) mm. Median (IQR) absolute x and y coordinate errors were 0.29 (0.52) and 0.38 (0.44) mm, respectively. Errors were largest after rotating the multielectrode holder to its "x"-shaped setup.

Conclusion: ME trajectory adjustments can be made accurately. In a considerable number of cases, errors exceeding 1 mm were found. Adjustments from the "+" setup to the "x" setup are most prone to inaccuracies.

Keywords: Deep brain stimulation; Intraoperative computed tomography; Microelectrode movement; Microelectrode recording.

Fig. 1

Multielectrode configurations. The figure illustrates the two BenGun configurations. The “+” setup allows for a 2-mm track adjustment in the x or y plane (anterior, posterior, medial or lateral). The “x” setup allows for a 1.4 mm adjustment in the combined x-y plane (anteromedial, anterolateral, posteromedial or posterolateral). The dotted lines represent the distance in millimeters from the central channel; this remains the same when rotating the holder. A, anterior; M, medial; P, posterior; L, lateral.

Fig. 2

Flowchart summarizing reported adjustments, illustrating how the number of analyzed adjustments was derived. Patients were included based on the availability of iCT data and if they had more than 1 track. The adjustments could only be analyzed if track adjustments were required, noted in patient charts, and if subsequent adjustments were monitored by iCT. SM, stage moves.

Fig. 3

Difference between intended and actual ME movement. The difference is shown between the intended (indicated by the arrows) and the actual ME tip location (the more lateral and anterior trajectory in the figure) following a 2-mm anteromedial move after the first MER track, achieved by rotating from the “+” to the “x” setup. Both trajectories are projected on a 3-tesla susceptibility-weighted image. Target in this case was the STN. Intended track coordinates were −10.1 (x), −1.34 (y) and −4.16 (z). ME tip coordinates were −11 (x), 0.10 (y) and −4.16 (z). Both tracks were corrected for the intended surgical target depth, which was 4.16 mm below the anterior-posterior commissure plane (z coordinate). The radial error between intended and actual ME movement was 1.69 mm. The ME ended up 0.91 mm more lateral and 1.42 mm more anterior than intended.