Frameless Deep Brain Stimulation Surgery: A Single-Center Experience and Retrospective Analysis of Placement Accuracy of 220 Electrodes in a Series of 110 Patients

Background: Proper lead placement is considered one of the key factors in achieving a good clinical outcome in deep brain stimulation (DBS), but there is still considerable controversy surrounding the accuracy of the frameless in comparison to the frame-based technique. Objective: We report our single-center experience with DBS electrode placement to evaluate the accuracy of the frameless stereotactic system. Methods: We prospectively analyzed the data of 110 patients who underwent DBS surgery for Parkinson disease, dystonia, essential tremor, or refractory epilepsy. The final targets (FTs) of the 220 leads were: subthalamic nucleus, globus pallidus pars interna, ventralis intermedius nucleus, and anterior nuclei of thalamus in thalamus. A bilateral stereotactic approach using a combined identification of target based on preoperative images (MRI and CT scan fusion) and intra-operative micro-electrode recording (MER) were done. We collected and compared the coordinates of planned target (PT), the definitive expected target (ET) during MER, and the effective final location (FT) of the lead using the postoperative CT. Accuracy was assessed by both vector error (VE) and deviation from the PT. Results: The mean and SD from PTs was 0.78 +/- 0.43 mm in the x direction, 0.68 +/- 0.41 mm in the y direction, and 0.76 +/- 0.41 mm in the z direction. Global VE was 1.43 +/- 0.37. Conclusion: Frameless systems appear to be a reliable and accurate technique.