T05. Pre-surgical assessment of drug-resistant insular and peri insular epilepsy: A single center experience

Introduction Epilepsy arising from the insula is widely regarded as a challenging type of seizure, probably owing to the deep-seated location of the insula and the extensive connections it makes with adjacent structures. In recent years, we have rapidly gained insights into insular epilepsy-related obstacles. Here, we describe a detailed analysis of the electro-clinical manifestations of this type of epilepsy using intra-cerebral recordings performed with Stereo-electroencephalography (SEEG). Methods We retrospectively analyzed 12 patients from our epilepsy program who underwent insular exploration using SEEG between June 2013 and June 2017. Patient information reviewed included demographics, clinical history, neurological examination; neuroimaging studies (Brain MRI, PET, Ictal SPECT), Scalp video-EEG, intracranial recordings with SEEG, histopathological findings, and surgical outcomes. Results 12 patients (M:F = 4:8; mean age, 32.5 years; range, 19–60 years) were found with seizures originating from either the insula alone or simultaneously originating from the insula and adjacent structures. One patient had a family history of epilepsy and another one had previous exposure to viral meningoencephalitis. Six patients had undergone prior surgery for epilepsy treatment. The mean seizure frequency was 4 seizures per week, and one patient experienced seizures daily. The most common aura was somatosensory sensation, followed by cephalic sensation in 4 and 3 patients, respectively. The commonest type of seizure was focal with impaired awareness in 10 patients. 50% of the patients showed a tendency for secondary generalizations, and 25% showed nocturnal predominance. Lesions were observed on brain MRI in 8 cases. Scalp EEG revealed different interictal discharge distributions: 5 patients showed localized frontotemporal spikes, 3 showed bilateral temporal spikes, and no spikes were detected in 4. The location of ictal onset could be localized in only 50% of patients. The most common scalp EEG ictal pattern was rhythmic delta activity (1–3 Hz). Subsequent SEEG showed six patients found to have a combination of clinical and subclinical seizures. SEEG clinical seizure onset from the insula alone was found in 50% of the patients (3 right, 2 left, 1 bilateral). The other patients presented with simultaneous onset from the insula and adjacent structures: 4 from mesial temporal structures, 1 temporal operculum, and 1 frontal operculum. The commonest SEEG ictal pattern was low voltage fast activity in 8 patients. Surgical resections guided by SEEG findings were performed in 5 patients and led to excellent outcomes; all these cases had Engle class 1 outcome at 6–24 months follow up. Conclusion We observed that it is not uncommon for seizures to simultaneously originate from the insula and adjacent structures. However, non-invasive EEG monitoring tools are likely insufficient to detect such simultaneous seizures. For the given sample, SEEG proved beneficial in providing optimal surgical outcomes.