Abstracts

Rationale: Stereo-electroencephalography (SEEG) is a minimally invasive, robust and precise method of localizing focal medically intractable epilepsy. While it has been in vogue for many decades in Europe, it is only recently being accepted as a strategy to localize epileptic networks in North America. Recently, a robot specifically designed for stereotaxis, has been available for SEEG electrode placement in the USA. The accuracy of this system in the clinical environment has never previously been validated. Methods: The SEEG implantation plan was arrived at after a comprehensive review of the non-invasive EEG, the imaging data and after an in-depth discussion of the hypothesized region/s of seizure onset. Pre-operatively, T1 weighted MRI scans with contrast with 1x1x1 resolution were obtained. Planning of entry and target points was performed using robotic stereotactic software (ROSANNA). 5 skull fiducials were placed in each patient and a volumetric contrasted CT scan was obtained and co-registered with the MRI scan. The ROSA robot was registered to the skull fiducials and SEEG electrodes (PMT) were implanted. A volumetric CT scan was obtained post implantation and also registered to the planning MRI scan to measure deviations from the plan. The lateral deviation of each electrode at the entry point and at the target point was measured and compiled. The surgical time of electrode placement was also computed. Results: Over a single year, 286 SEEG electrodes were placed in 23 patients. There were no complications (hemorrhages, swelling or infection) associated with electrode placement. Close review of the post-op imaging did not show any hemorrhages. The mean lateral error at the entry point was 0.6 mm (stdev 0.5) and at the target it was 0.94 mm (stdev 0.9). In all but 19 electrodes (6.7%), the error at the target was less than 2.5 mm. The Insula was targeted using a parietal entry site and placement in either the anterior or posterior long gyrus, in 6 instances, with no complications. The average time for implanting each electrode was just under 9 minutes. Conclusions: Robotic SEEG is a precise and rapid strategy for implanting electrodes for intracranial monitoring to pinpoint seizure foci. The use of skull fiducials, and careful planning may enable more precise placement and lower complication rates than other registration techniques.