Abstract Details

Title Localization of Inter-ictally Silent (IIS) Drug Resistant Focal Epilepsies (DRE)

Topic Epilepsy/Clinical Neurophysiology (EEG)

Presentation(s) P16 - Poster Session 16 (8:00 AM-9:00 AM)

Poster/Presentation
Number 10-002

Objective To localize anatomic origins of focal epilepsies that lack inter-ictal epileptiform discharges (IEDs) [referred here as interictally silent (IIS)] on scalp EEG.

Background Even though IIS epilepsies represent 8 - 17% of focal epilepsies, literature on these epilepsies is scant and they have not been well-described.

Design/Methods Adults evaluated in the epilepsy monitoring unit (EMU) from 01/01/2015 to 12/31/2019 were screened to identify patients monitored for > 48 hours with IIS EEGs and at least one clinical seizures recorded on EEG. Patient with Engel 1 outcome after ≥1year of follow up of epilepsy surgery were included. Patients with prior EMU or routine EEGs showing IEDs were excluded.

Results Of 249 patients with IIS epilepsies, 31 patients [mean age 33.2+11.6 years; 16 (51.6%) females] with Engel I outcome at > 1 year after surgery were included. Eighteen (58.1%) patients had lesional MRIs (17 unilateral and 1 bilateral). Twenty-one (67.7%) underwent magnetoencephalography of whom 17 (81.0%) were IIS and 5 (19%) had IEDs. Fourteen (45.1%) patients underwent intracranial evaluation. Twenty-eight (90.3%) underwent resective surgeries and 3 had laser ablations. Nineteen (61.3) had surgery on the right side. Two-thirds (64.5%) of epilepsies localized to either mesial (n=9; 29.7%) or neocortical (n=2) temporal (n=11,35.5%) and opercular (n=9,29.0%) regions. The remaining epilepsies localized to the cingulate/mesial frontal (n=4,12.9%), orbitofrontal (n=3,9.7%), middle frontal gyrus (n=2) and mesial occipital (n=2) regions. Pathology showed malformation of cortical development among 17 (60.7%) patient, including 2 with associated hippocampal sclerosis (HS). Other pathologies were HS(n=3), gliosis(n=4), glial tumor(n=1), cavernoma(n=1), infarct (n=1) and reactive astrocytes (n=1).

Conclusions Majority of IIS focal epilepsies localize to mesial temporal or opercular regions. Some localize to other deeper regions including cingulate, mesial frontal, orbitofrontal and mesial occipital regions. These regions should be considered primary epileptogenic zone candidates during epilepsy surgery evaluation of IIS epilepsies.

Authors/Disclosures
Ifrah Zawar, MD (University of virginia) PRESENTER	The institution of Dr. Zawar has received research support from Alzheimer's association. The institution of Dr. Zawar has received research support from American epilepsy society . The institution of Dr. Zawar has received research support from NIH. The institution of Dr. Zawar has received research support from University of Virginia.
	No disclosure on file
Richard C. Burgess, MD, PhD (Cleveland Clinic, Dept of Neurology)	Dr. Burgess has nothing to disclose.
Andreas V. Alexopoulos, MD, MPH (Cleveland Clinic)	Dr. Alexopoulos has nothing to disclose.
Vineet Punia, MD (Cleveland Clinic)	Dr. Punia has nothing to disclose.

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