Correlating lesion localization within the functional cortical networks in sleep related epilepsy caused by focal cortical dysplasia type II.

BACKGROUND: To investigate whether the co-localization of focal cortical dysplasia (FCD) type II within the distributed cortical networks and the presence of alteration in the subcortical structures were associated with sleep related epilepsy (SRE) in patients with FCD type II. METHODS: Epileptic patients with histologically proven FCD type II between March 2012 and June 2023 were enrolled. FCD volumes, anatomical locations, and functional network locations were determined. Voxel-based volumetric and vertex-wise shape analyses were performed on subcortical regions including the thalamus, caudate, putamen, pallidum, hippocampus, and amygdala. The volumes of thalamus nuclei were also calculated. RESULTS: A total of 108 patients were included. Among them, 55 were categorized as SRE and 53 as non-SRE. FCD type II was predominantly observed in the frontal lobe and default mode networks. Multivariate analyses revealed that smaller FCD lesions (p = 0.035) and the absence of an aura (p = 0.041) were independently associated with SRE. However, FCD within the dorsal attention network (p = 0.048) was associated with non-SRE. No statistical difference was found between the SRE and non-SRE groups in terms of the volume of the thalamus or individual thalamic nuclei. Additionally, no regional shape alterations were observed in patients with SRE compared to those with non-SRE. CONCLUSIONS: Our study identifies distinctive clinical characteristics and specific co-localized neural network associations between SRE and non-SRE in patients with FCD type II. Recognizing these distinct features is crucial, as it enables further research and enhances in improving the diagnosis of FCD type II.