Outcomes of Bilateral Diagnostic Intracranial EEG in Non-Lateralized Treatment Resistant Epilepsy (P4.196)

Objective: To characterize efficacy and risks of diagnostic bilateral intracranial electroencephalography (bICEEG) in treatment-resistant epilepsy (TRE) patients with poorly lateralized epileptogenic zone (EZ) on non-invasive studies. Background: Patients with TRE are candidates for epilepsy surgery if the EZ is localized and deemed resectable. For cases with discordant non-invasive studies, bICEEG may definitively lateralize the EZ to identify surgical candidates. Methods: We retrospectively reviewed all 208 bICEEG cases at New York University (NYU) between 1994 and 2013. Endpoints included: progress to resection, Engel outcome, and peri-operative complications. Results: Of 208 patients, 19 were lost to follow-up. For 60[percnt], bICEEG lateralized the EZ and they progressed to therapeutic resection or further regional ICEEG. Subdural and depth electrodes were routinely used together but only the number of depth electrodes positively correlated with progress to resection and depth electrode use was not greater in temporal lobe cases. Forty-eight percent who progressed to resection were seizure free at last follow-up (mean 5.4yrs) compared with 13[percnt] of patients who did not have resection (mean 5.6yrs). Pre-operative seizure frequency greater than 1/day was associated with worse post-operative seizure control. The most common complication was infection requiring surgical intervention; occurrence was 3.1[percnt]. Rates of superficial infection, DVT, pulmonary embolism, stroke, and hemorrhage were each below 1[percnt]. Conclusions: At NYU, 60[percnt] of patients with TRE who underwent bICEEG progressed to EZ resection and 48[percnt] of these cases were seizure free. The risks of bICEEG monitoring are similar to our unilateral invasive monitoring. We conclude that bICEEG extends the benefit of epilepsy surgery to poorly lateralized TRE patients. Future analysis will determine the relative predictive value of seizure semiology, vEEG monitoring, MRI, MEG, and PET to progress to resection and Engel outcome in this series; as well as determine how depth electrodes augment subdural monitoring. Disclosure: Dr. Hill has nothing to disclose. Dr. Rubin has nothing to disclose. Dr. Tyagi has nothing to disclose. Dr. Theobald has nothing to disclose. Dr. Silverberg has nothing to disclose. Dr. Miceli has nothing to disclose. Dr. Dugan has nothing to disclose. Dr. Carlson has nothing to disclose. Dr. Doyle has nothing to disclose.