Anatomical categorization of insulo-opercular focal cortical dysplasia and the spatial patterns of stereoelectroencephalography.

Abstract

Objective: This study was undertaken to anatomically categorize insulo-opercular focal cortical dysplasia (FCD) lesions according to their location and extent, and to summarize corresponding stereoelectroencephalographic (SEEG) patterns to guide preoperative evaluation and surgical planning.

Methods: Patients who underwent epilepsy surgery for insulo-opercular FCD between 2015 and 2022 were enrolled. FCD lesions were categorized into insular, peri-insular, opercular, and complex types based on their location and extent, as ascertained from electroclinical and neuroimaging data. SEEG signals from the seizure onset electrodes were collected for quantitative analysis. The normalized interictal spike counts, high-frequency oscillation (HFO) counts, and ictal epileptogenicity index (EI) values of the insular and opercular channels were calculated. The spatial patterns of the spike counts, HFO counts, and EI values were analyzed. Cluster analyses utilizing spike counts, HFO counts, and EI values were performed for automatic categorization, and the results were compared with the manual categorization from the preoperative evaluations.

Results: A total of 53 patients were included, comprising 10 insular, 17 peri-insular, 24 opercular, and two complex cases. Thirty-eight patients were included in the quantitative SEEG analysis. Spike, HFO, and EI analyses indicated that in insular FCDs, the values of the three parameters were higher in insular channels than in opercular channels. In peri-insular FCDs, the values in insular and opercular channels were comparable, whereas in opercular FCDs, the values were higher in opercular channels than in insular channels. The accuracies of the cluster analysis based on the spike counts, HFO counts, and EI values were 71.05% (27/38), 76.32% (29/38), and 86.84% (33/38), respectively. Surgical strategies were proposed according to the anatomical categorization, achieving a favorable postoperative seizure-free rate of 84.91%.

Significance: Insulo-opercular FCDs can be categorized into insular, peri-insular, opercular, and complex types. SEEG patterns can facilitate the automatic categorization of insulo-opercular FCDs, thereby enhancing preoperative planning and surgical outcomes.