Abstracts

Rationale: There is a limited literature of confirmed cases of insular onset seizures and propagation patterns. A feature of this subset of focal epilepsy is the rapid propagation of seizures from insular lobe to other cerebral regions, including contralateral insula. The aim of this study is to analyse ictal SPECT in a group of patients with insular epilepsy. Methods: From a database of 40 patients who underwent stereoelectroencephalography (SEEG) between December 2012 and May 2016, we collected patients with confirmed insular onset epilepsy. We examined SPECT hyperperfusion pattern with SISCOM threshold at 2 standard deviation and the EEG ictal propagation with SEEG evaluation Results: We identified 6 patients, 4 female. Median age of seizure onset was 9 years old (8 months to 15 years). All patients reported an aura; 4 somatosensory (limb, face, throat), 2 gustatory, followed in all cases by either choking/gagging, bilateral asymmetric tonic seizures or hemiclonic seizures: one patient had also automotor seizures. Four of six patients had epilepsy surgery with a tailored resection of opercular and insular cortex and are seizure free at 3 to 25 months follow up. Histopathology showed cortical dysplasia (Type 1a=1, 2a=2) and tuberous sclerosis (n=1). All of them underwent ictal SPECT as part of presurgical evaluation. The median time of injection was 8.4 seconds for 5 patients (3-17 sec), with a seizures median duration of 42 seconds (11-85 sec). One patient was injected at 43s with seizure duration 88s. In those 5 with short injection times, the insula cortex showed focal hyperaemia in three patients, all of them contralateral to the ictal onset. Other sites with hyperaemia included the basal ganglia in three patients; bilaterally with higher hyperperfusion to contralateral side in two of them and ipsilateral to ictal onset zone in one patient. One patient had focal hyperaemia in the contralateral middle temporal gyrus. One patient had bilateral insula implantation, and the inter-hemispheric transit time was 20-30ms between bilateral insular interictal epileptiform discharges and 300-500ms for ictal onset. Conclusions: The classically described gagging sensation in insular epilepsy is uncommon. Majority of patients have somatosensory or gustatory aura. Ictal SPECT often falsely localise to the contralateral insula probably related to the rapidly interhemispheric propagation. Funding: No funding was supported for this abstract