Abstracts

Rationale: Insular seizure semiology may mimic the symptomatology of temporal/frontal lobe seizures. Recently, stereo-EEG technology has demonstrated effective identification of insular onset origin seizures. We aimed to analyze the electro-clinical involvement, as well as surgical outcome, complications, and histopathology results.  Methods: We retrospectively analyzed 121 adult patients who underwent intracranial EEG monitoring for refractory focal epilepsy between January 2010 until December 2018. Demographic data, structural imaging, pre-implantation seizure onset zone localization hypothesis, results from intracranial EEG, surgical complications, histopathology results, and outcomes were obtained.  Results: Sixty-two patients with electrographic insular involvement seizures, 30 (48%) were found to have insula as primary seizure onset and, of the latter group, 19 (63.3%) were lesion negative MRI’s. Four (13.8%) had history of previous epilepsy surgery. The pre-implantation hypothesis was frontal, orbitofrontal, operculo-, insular, peri-insular, or temporal lobe. Seventeen (58.6%) had bilateral depth and 12 (41.4%) had unilateral implantation. Six out of these 29 patients had additional electrodes implanted during course of SEEG, 1 case had additional strips and grids and 2 had strips together with depth. Total of 5 (17%) patients had post-implantation complications as follows: SDH (1), intracerebral hematoma (1), extradural hematoma (2), and broken electrode (1). Twenty-four (82.7%) of patients had prominent interictal discharges in the insula. The predominant ictal pattern was low voltage fast activity. 18 patients had spread from insula to adjacent regions, of which 5 had contralateral spread with a mean of 8.6 seconds. Twenty-one patients underwent surgery, of which only 8 patients had insular resection and 2 declined. Histopathology showed cortical dysplasia (2), hippocampal sclerosis (5), deposition of corpora amaylacea (1),  non-specific findings (19), and 2 specimens were lost. Eleven patients were Engel class I and 3 were Engel class II at mean follow-up of 24 months.  Conclusions: We observed that SEEG was a beneficial tool in determining insular involvement and providing optimal surgical outcome particularly in patients with nonlocalising semiology and nonlesional imaging.  Funding: No funding