Abstracts

Rationale: To analyze adverse outcomes associated with stereoelectroencephalography (sEEG) at a single pediatric tertiary care epilepsy center. Methods: Retrospective analysis of 47 patients who underwent sEEG implantation at our institution between January 2015 and June 2019 and comparison with other published data. Results: Forty-seven patients underwent sEEG implantation for presurgical monitoring. Mean duration of follow-up was 16 months (IQR: 7-24). Seven (15%) had undergone a previous resection. Presumed etiologies were structural congenital (n=31;66%); structural acquired (n=9;19%); infectious (n=2;4%); genetic (n=3;6%), and unknown (n=2;4%). Amongst the structural congenital etiologies, focal cortical dysplasia was the most common (n=23;74%). Robot-assisted electrode placement was used in the majority (n=42; 89%). There was a total of 626 electrodes initially implanted, with a median of 13 electrodes implanted per patient (IQR:11.5-15). Additional electrodes were implanted based on initial sEEG findings in 6 patients. There was a total of 34 additional electrodes placed with an average of 6 electrodes added per patient (IQR:5.25-6.75). All patients had preoperative MRI with contrast for trajectory planning and all, but one patient had a preoperative CT scan with fiducials for co-registration purposes. Every patient had a post implantation CT scan. Skiving was noted in 4 (8.5%) patients, corresponding to 0.6% of implanted electrodes. Intracranial hemorrhage, including asymptomatic hemorrhages, was noted on the initial post implantation CT in 11 (23.4%) patients. There was additional post-operative hemorrhage noted in 4 out of 6 patients who underwent additional electrode placement, including 2 patients with initial post-operative hemorrhage. This corresponds to a total post-implantation hemorrhage rate of 28.3% (15/53) and a per electrode hemorrhage rate of 2.3% (15/660). Hemorrhages were subdural in 7; intraparenchymal in 4, and subarachnoid in 4. Only two were symptomatic – one with transient symptoms and one death attributed to an unrecognized intraoperative subdural bleed of > 5 mm with midline shift, edema and herniation without intraoperative vital sign changes. The rate of symptomatic hemorrhage for number of total implantations was 3.8% (2/53), for a risk of 0.3% per electrode. An electrode failure, defined as fracture or failure to record, occurred in 11 electrodes implanted with a total electrode failure rate of 1.6%. Resection was completed in 25 of 45 (55.5%) patients with follow-up after sEEG monitoring. 64% (n=16) were seizure free at last follow up. Of the 20 (44.4%) who did not undergo resection, in 7 (35%) this was due to involvement of eloquent cortex and in 9 (45%) the captured seizures were non-localizing or seizures were not captured. In 4 patients, surgery was scheduled but not yet performed. There were no infections related to sEEG placement. Conclusions: The risk of hemorrhage at our center after sEEG implantation is comparable to other recently published reports. The majority of hemorrhages represented asymptomatic subdural or subarachnoid hemorrhages, although there was one patient with transient neurologic symptoms and one death. About half of patients who underwent sEEG implantation underwent resection, with seizure freedom rates similar to other published studies. Funding: No funding