Abstracts

Rationale: The transition of North American epilepsy surgery centers from subdural electrode implantations to stereoelectroencephalography (SEEG) has been largely facilitated by technological advances including robots. Our center has recently demonstrated that the transition to robotic SEEG is safe and reduces operating room time [1]. Here, we analyze application accuracy in a consecutive series examining the impact of anatomical and patient-related factors.

Methods: Application accuracy was retrospectively computed for each electrode in a consecutive series of robotic SEEG implantation surgeries. Specifically, Euclidean distance and radial distance (which better accounts for the error along a trajectory), were calculated between the planned point (based on the preoperative structural MRI scan) and the actual point (measured using postoperative computed tomography) of the electrode trajectory. Results were reported using median distance with interquartile range (IQR; in brackets). The effect of anatomy and patient factors was also examined.

Results: Data from 68 implantation surgeries (776 electrodes; mean: 11.4 per patient) were analysed with demographic data described in Table 1. Median entry and target point error were 1.17 (IQR: 0.75-1.70) and 1.87 (1.29-2.59) mm respectively. The least accurately targeted structures were the temporal pole and posterior insula: 2.54 (1.50-3.35) and 2.73 (2.10-3.35) mm respectively. The most accurately targeted structures were the posterior and anterior supplementary somatosensory motor areas: 1.10 (0.86-1.28) and 1.55 (1.08-2.46) mm respectively. The results for the most common targets are presented in Table 2. Target error was worse in the context of prior cranial surgery at 1.44 (0.93-2.09) mm compared to de novo implantations 1.57 (0.90-2.46) mm (Wilcoxon testing, p < 0.05). Longer trajectories also resulted in increased error. Radial error was significantly less than Euclidean error for entry and target points at 0.99 (0.61-1.48) and 1.35 (0.78-1.96) mm respectively (Wilcoxon testing, p < 0.01). There was one small asymptomatic cortical intracerebral hematoma along the entry of the electrode (1.5% of patients; 0.1% of trajectories). There were no adverse surgical outcomes from surgery.