Accuracy and Utility of Frameless Stereotactic Placement of Stereoelectroencephalography Electrodes

Successful surgery for epilepsy hinges on identification of the epileptogenic focus. Stereoelectroencephalography (sEEG) is the most effective way to identify most seizure foci. There are multiple methods of inserting depth electrodes, including frame-based, frameless, and robot-assisted techniques. Studies have shown the accuracy of frame-based and robotic-assisted techniques to be statistically similar, while only one study has detailed the frameless sEEG insertion technique.

Patients underwent placement of sEEG depth electrodes using frameless stereotaxy from September 2019 to September 2021 at Geisinger Medical Center by a single surgeon. Seizure history, electrode placement accuracy relative to the planned trajectories, surgical times, success rate of identifying the epileptogenic focus, and subsequent seizure control rates after surgical treatment were documented.

Data were available for 21 patients and 181 electrodes inserted using the VarioGuide frameless stereotactic system. Each insertion took an average of 14.5 minutes per lead. Average entry variance was 2.7 mm with an average target variance of 4.6 mm. The epileptogenic focus was identified in 19 of 21 patients, and further surgical treatment was performed in 18 of 21 patients (85.7%).

VarioGuide frameless stereotaxy for sEEG placement is comparable to frame-based and robotic-assisted techniques with statistically similar rates of epileptic focus identification. Lead placement accuracy is slightly lower and time per lead is slightly higher relative to robot-assisted surgeries. When a robot system is unavailable, surgeons can consider using a frameless stereotactic technique for sEEG insertion, allowing patients to benefit from a similarly high rate of epileptic zone identification.