Abstracts

Rationale: To investigate the characteristics of seizure semiology, electrographic features, etiology and outcomes in patients with epilepsy who underwent resection of the orbitofrontal region (OFR) for the treatment of epilepsy in our center. Methods: We performed a review of a consecutive case series of patients undergoing orbitofrontal region (OFR) resections for epilepsy between 2005 and 2018, with longitudinal follow-up. We included all cases that underwent partial or complete resection of the OFR with or without resection of other brain regions, with or without intracranial EEG (icEEG). Outcome was assessed using the Engel Outcome Scale. Results: Twenty-five patients (65% male), mean age of 33 years (SD=16), underwent OFR resection. Mean duration of epilepsy prior to OFR resection was 16 years (SD=13) and 13 (52%) had prior brain surgery. Pre-surgical workup included scalp video-EEG, MRI, and neuropsychological testing. 20% of patients had PET scans, 56% had MEG scans, and 8% had ictal SPECT. Twenty of 24 (83%) patients had seizures recorded during their phase I evaluation. Nine (45%) were lateralized and 10 (50%) were localized to regions that included the frontal lobe. Auras were reported in 16 (67%) patients, and were variable, including metallic taste, dizziness, deja-vu, cephalic and autonomic. Seizures occurred out of sleep in 13 (52%). Semiology consisted of versive movements in 32%, vocalization in 28%, hand automatisms in 20% and oral automatisms in 28%. 52% had hypomotor seizures (including "staring" or "behavioral arrest"). Overt hypermotor behavior was not seen in any patient, although one patient was described as "agitated" and another as "restless".MRI showed frontal lesions in 15 (63%), and all but one patient who underwent PET imaging had frontal lobe hypometabolism (80%). MEG yielded additional localizing information to the MRI in 2 cases (14%). Sixteen (64%) cases underwent icEEG evaluation. 11 (69%) had subdural electrodes, 4 (25%) had SEEG and 1 (6%) had both. Nine (56%) had right sided implantation, 4 (25%) had left sided implantation, and 3 (19%) had bilateral implantation. icEEG revealed OFR onset in 10 (63%) cases. 63% of patients who underwent icEEG had no lesion in the frontal lobe on MRI. 100% of patients who had OFR resection without icEEG had identifiable lesions in the frontal lobe on MRI. Intraoperative post-resection ECoG recordings were performed in the majority of cases (88%), leading to additional resection in 8 (36%). Residual spikes were seen but not resected in 8 cases (36%). Histopathological analysis revealed focal cortical dysplasia (FCD) type 1 (4%), FCD type 2b (4%), tumor (8%), vascular disease (12%), post-traumatic changes (36%), and non-specific gliosis (36%).Median follow up after surgery was 27 months. Fifteen patients (60%) had good outcome (Engel Outcome Scale of I or II). There was no significant difference in outcomes between the 11 patients with pure OFR resection (64% good outcome), compared to the 14 patients who had OF plus other regions resected (57% good outcome) [p-value 0.99; OR 1.298 (CI: 0.1997, 9.1143)]. Conclusions: This is the largest series of OFR resections in the literature. The majority of our patients reported auras, contrary to previous studies. Seizures often occurred out of sleep, as seen commonly in frontal lobe epilepsy. Outcomes were not different between patients who received pure OFR resections compared to those with resections extending beyond the OFR. Long-term outcomes in this series supports the targeting of the OFR for resection when indicated by non-invasive testing and/or augmented by data provided by icEEG. Funding: None