Abstracts

Rationale: Image-guided placement of intracranial surface and depth recording electrodes for the characterization of epileptic foci was first promoted forty years ago (Talairach, Bancaud et al., 1974). This was a frame-based technique that made use of intraoperative angiography with the aim of understanding the initiation and three-dimensional propagation of epileptic discharge while avoiding vascular complications. Stereoelectroencephalography (SEEG) has been in use at the Montreal Neurologic Institution since 1976 with very low morbidity (Tanriverdi et al, 2009). The procedure has been in constant evolution to take advantage of innovation in imaging and computer technology. MRI-compatible commercial electrodes (DIXI, Microtechniques, France) have been in use since 2007 and a Robotic Surgical Assistant (ROSA, Medtech, France) has been used since 2011. Previous work has shown a greater degree of accuracy with the robotic-assisted technique (Chatillon et al, 2011). Methods: A review of patients who underwent implantation of intracranial electrodes for the exploration epilepsy by the author was performed to report upon the technique and examine for complications. The study was restricted to patients implanted with fully MRI-compatible SEEG in order to review MRI abnormalities on all patients with electrodes in situ. Results: Twenty-eight cases were identified; 16 cases used a manual technique of frameless stereotaxy and 12 cases used robotic assistance. The indication for implantation varied from multi-lesional to non-lesional pathology. In all cases the technique utilized fusion of both CT-contrast and MRI-gadolinium enhanced images without traditional angiography. The total number of electrodes implanted was 287. The average number of electrodes implanted per patient was 10.25. Frameless manual stereotaxy was used on the first 16 cases to place 160 electrodes. Robotic assistance was used on the last 12 cases to place 127 electrodes. There was no mortality, no infection and no new neurologic deficit in this series. One case using frameless manual stereotaxy and one robotic-assisted case demonstrated MRI abnormalities associated with the implantation. Thus the rate of radiologic abnormality was 7.14% per patient or 0.69% per electrode. Conclusions: The extremely low rate of clinical morbidity associated with this technique is in keeping with previous reports from our institution. The rate of radiologic (MRI) abnormality is a novel finding derived from early experience with MRI-compatible electrodes and its significance needs further consideration. The combination of MRI-compatible electrodes with robotic assistance seems a safe and promising avenue in epilepsy surgery.