In 7 patients with refractory epilepsy, 89 depth electrodes were implanted using a frameless stereotactic drilling technique. Each electrode was planned on a preoperative magnetic resonance and computed tomographic scan, and verified on postoperative computed tomographic scan. After fusion of preoperative and postoperative imaging, the accuracy for each electrode was calculated as the Euclidean distance between the planned and observed position of the electrode tip.
The median Euclidean distance between planned and observed electrode implantations was 3.5 mm (95% confidence interval, 2.9–3.9 mm) with a range of 1.2–13.7 mm.
In this study, we showed that the in vivo accuracy of our frameless stereotactic drilling technique, suitable for stereoelectroencephalography depth electrode placement and diagnostic brain biopsies, was 3.5 mm.