Abstracts

Rationale: Use of intraoperative MRI (iMRI) has been used in tumor surgeries and in epilepsy surgeries involving focal cortical dysplasia. However, there is limited literature on the role of iMRI in hemispherectomies and corpus callosotomies in the pediatric population. Therefore, we aim to evaluate the utility of iMRI in these populations. Methods: Chart review of all patients with refractory epilepsy who underwent functional hemispherectomy (HE) or corpus callosotomy (CC) between 2015 and 2016 at Boston Children's Hospital was performed. Demographics, seizure history, including neuroimaging findings, whether iMRI was obtained, and seizure outcome data were obtained for all patients. Results: Of 16 patients who underwent HE, iMRI was performed in 62% (10/16) of cases. In 70% (7/10) of these, this facilitated further disconnection by clarifying anatomical/vascular landmarks, such as in patients with hemimegalencephaly or Sturge Weber syndrome. Seizure freedom was attained in 5 of these 7 patients. Over a median follow-up of 22 months (range: 2-37 months), 69% (11/16) of patients had Engel 1a outcomes, including 6/10 patients who underwent iMRI, and 5/6 patients who did not undergo iMRI (p=0.20). In patients who did not achieve seizure freedom but underwent iMRI, known bilateral disease was present in 2 patients, a possible small band of residual corpus callosum was noted in 1 patient only on later MRI that was not noticeable on iMRI, and post-surgical imaging in 1 patient showed signal abnormalities in the contralateral hemisphere. Of 11 patients who underwent corpus callosotomy, either complete or anterior two-thirds, 55% (6/11) underwent iMRI. Persistent connection was reported in two patients. Disconnection was completed in one patient, but not in the second patient due to risks of excessive bleeding. Over a median follow-up of 11 months (range: 2-34 months), 91% (10/11) had Engel 3 outcomes. Although there was no difference in outcomes between those who underwent iMRI and those who did not, the varying degrees of seizure reduction resulting from this palliative procedure are not captured by the Engel scoring system. Conclusions: In patients who underwent functional HE, iMRI was beneficial in clarifying the extent of disconnection and in aiding the surgical decision making in multiple ways. In the cohort of patients who underwent corpus callosotomy, completion of disconnections was confirmed by iMRI in a majority of patients. Differences in outcome following corpus callosotomy with and without iMRI may not have been evident due to the palliative nature of this procedure. Further studies with a larger cohort are needed. Funding: None