Minimizing Brain Shift in Stereotactic Functional Neurosurgery

BACKGROUND: Stereotactic functional neurosurgical interventions depend on precise anatomic targeting before lesioning or deep brain stimulation (DBS) electrode placement. OBJECTIVE: To examine the degree of subcortical brain shift observed when adopting an image-guided approach to stereotactic functional neurosurgery. METHODS: Coordinates for the anterior and posterior commissural points (AC and PC) were recorded on thin-slice stereotactic magnetic resonance imaging (MRI) scans performed before and immediately after DBS electrode implantation in 136 procedures. The changes in length of AC-PC and in stereotactic coordinates for AC and PC were calculated for each intervention. In patients with Parkinson disease undergoing bilateral subthalamic nucleus (STN) DBS with at least 6 months of follow-up, pre- and postoperative scores of the motor part of the Unified Parkinson's Disease Rating Scale (UPDRS-III) were reviewed. RESULTS: Mean (SD) change in AC-PC length (MC-PC) was 0.6 (0.4) mm. There was no statistically significant difference in MC-PC between groups when examining anatomic target subgroups (P=.95), age subgroups (P=.63), sex (P=.59), and unilateral versus bilateral implantation (P=.15). The mean (SD) vector changes for the comnnissural points were: -0.1 (0.3) mm in X, -0.4(0.6) mm in Y, and -0.1 (0.7) mm in Z for the AC; and -0.1 (0.3) mm in X, -0.2 (0.7) mm in Y, and 0.0 (0.7) mm in Z for the PC. There was a negligible correlation between the magnitude of brain shift and percentage improvement in UPDRS-III off-medication in patients undergoing STN DBS for PD (R-2<0.01). CONCLUSION: Brain shift has long been considered an issue in stereotactic targeting during DBS procedures. However, with the image-guided approach and surgical technique used in this study, subcortical brain shift was extremely limited and did not appear to adversely affect clinical outcome.