Anterior Versus Posterior Insular Epilepsy: Correlations with Semiology Based on Stereoelectroencephalography

To characterize insular seizure semiology and correlate with stereoelectroencephalography (SEEG) seizure onset in a well-defined cohort, in particular examining differences between anterior and posterior insular seizures.

We documented all semiological signs and the timing of emergence for 45 patients with SEEG-confirmed insular epilepsy, along with the precise location of the seizure onset zone (SOZ) within the insula. Semiological signs and other non-invasive data were compared between those with anterior and posterior insula SOZ, with more detailed insular subregion description when appropriate. Co-occurrence patterns of insular semiological signs were also investigated.

A total of 87% reported auras and the corresponding insular SOZ demonstrated an anterior-to-posterior gradient by aura type. The absence of aura was significantly associated with an anterior insula SOZ (p = 0.01). Late grunting/moaning (p = 0.07), symmetric mouth elementary motor (p = 0.1), blinking (p = 0.05), and chewing/repetitive swallowing (p = 0.09) also suggested an anterior insula SOZ. Unilateral non-painful somatosensory aura (p = 0.07) and early arm/hand elementary motor (p = 0.1) suggested a posterior insular SOZ.

We report the characteristics and semiological features in a large cohort of primary insular epilepsy patients. The type of aura is crucial for identifying the SOZ and the timing of semiological emergence contributes to the anatomo-electro-clinical localization of an insular SOZ. These findings can enhance identification of insular epilepsy, making targeted curative treatment feasible. ANN NEUROL 2025;98:1111-1124.