Physician Mary Bridge Children's Hospital, Washington
Rationale: Seizure outcomes following hemispherectomy are generally good, with reported 50-80% of patients achieving seizure freedom post-operatively. Studies have shown that pre-operative and post-operative interictal discharges provide poor and uncertain prognosticative value, respectively. In this study, we aim to characterize the prognostic value of the evolution from pre-operative to post-operative seizures in functional hemispherectomy. Methods: We retrospectively reviewed 22 patients who underwent hemispherectomy at our institution (2010-2020) who had both pre-operative and post-operative EEGs available for review. All EEGs were reviewed for ictal and interictal findings, and categorized as ipsilateral to the lesion, independently arising from the contralateral side, and/or generalized. Seizure outcomes were classified according to the Engel Surgical Outcome Scale. Results: Of 22 patients, 18 (82%) became seizure free (Engel Class IA), with a mean clinical follow up of 4.1 years (range 0.3-9.5 years) after surgery. Of pre-operative EEGs, 41% had seizures, 100% had ipsilateral interictal discharges, and 36% had contralateral interictal discharges. Of post-operative EEGs, obtained on average 1.6 years (range 5 days-7.9 years) after surgery, 14% had seizures, 73% had ipsilateral interictal discharges, and 23% had contralateral interictal discharges. Of the 14% who had seizures on post-operative EEG, all were free of clinical seizures. On paired EEG review, 13 patients (59%) demonstrated resolution of either ictal or interictal discharges, 2 (9%) demonstrated an emergence of contralateral interictal discharges, and 7 (32%) demonstrated no change. Of the four patients in this cohort who did not achieve Engel Class IA seizure freedom, three were Engel Class IB and one was Engel Class IIB. Their EEGs were not predictive of their outcomes, with three having no seizures on either pre- or post-operative EEG, and one having resolution of pre-operative seizures. All patients who had persistent postoperative seizures achieved Engel IA. Conclusions: Seizure outcomes after hemispherectomy are generally excellent, with 82% in our cohort achieving seizure freedom and 100% achieving Engel Class I or II. The presence of ictal or interictal findings on pre- and post-operative EEGs independently, as well as the evolution of EEG findings over time was not predictive of outcomes Funding: Please list any funding that was received in support of this abstract.: None
