Abstracts

Rationale: Stereoelectroencephalography (SEEG) has been in regular use at the Montreal Neurological Institute since 1972. It has been in constant evolution to adapt to technological advances in materials, imaging and robotics. MRI-compatible electrodes were introduced in our centre in 2007 and a robotic surgical assistant in 2011. Here we report the technique, safety and advantages of the current method of SEEG implantation at the MNI. Methods: We retrospectively reviewed patients who underwent SEEG implantation by the senior author. The Research Ethics Board of the Montreal Neurological Institute and Hospital approved the review (NEU-14-101). The technical, clinical and radiological complications as well as the post-implantation outcome were analyzed. Only patients implanted with MRI-compatible electrodes were included in order to review MRI abnormalities with electrodes in situ. Results: Fifty-three patients were implanted with 550 electrodes, averaging 10.4 electrodes per patient. Manual frameless stereotaxy was used in 20 patients (184 electrodes) until the advent of robotic assistance which was used for the remaining 33 patients (366 electrodes). The electrodes were implanted for an average duration of 15 days. There was no mortality, no infection and no new neurologic deficit in any patient. Two patients had a technical complication of electrode insertion with a superficial screw plunge without clinical consequence. Four patients demonstrated asymptomatic MRI abnormalities associated with implantation (radiological abnormality rate of 7.54% per patient or 0.72% per electrode). Among the 49 patients in whom the SEEG findings were finalized, 31 (63%) underwent therapeutic intervention (29 resections and two thermocoagulations). The MRI with electrodes in situ were used for navigation in all 29 who underwent resection and yielded histopathological diagnosis of focal cortical dysplasia in15 MRI-negative patients. Conclusions: Our current technique of SEEG implantation was associated with no clinical morbidity although not without technical complication or radiologic (MRI) abnormalities. We should therefore remain vigilant in refining the technique and minimize the number of electrodes required to answer a well-developed pre-operative hypothesis regarding the seizure onset zone. The use of MRI-compatible electrodes helped in localizing MRI-negative lesions such as focal cortical dysplasia. Neuronavigation using MRI with SEEG electrodes in situ was useful to tailor definitive resections in these patients. Funding: H.M.K. is supported by the Mark Rayport and Shirley Ferguson Rayport Fellowship for epilepsy surgery of the Montreal Neurological Institute and Hospital.