Ictal Epileptogenic Network Differences in Posterior Cingulate Epilepsy Subtypes Based on SEEG

To compare differences in ictal propagation between epileptogenic networks between posterior cingulate cortex (PCC) epilepsy and retrosplenial cortex (RSC) epilepsy and to elucidate their network-level pathophysiological characteristics.

A total of 18 patients with confirmed PCC or RSC-related epilepsy were enrolled in this study. We calculated directed functional connectivity across preictal, ictal onset, and propagation phases based on pairwise nonlinear regression (h² coefficient). Using graph theory and linear mixed-effects models, we quantified network topology and dynamic propagation patterns of epileptogenic networks.

Neuropsychological tests showed significantly poorer visual recall in patients with RSC epilepsy (p = 0.030). During the propagation phase, the ipsilateral mesial temporal structures showed significantly greater node out-strength than in-strength, acting as a secondary driver of seizure spread (p = 0.004). The lateral temporal cortex acted as a signal receiver with dominant in-strength (p = 0.015). RSC epilepsy also showed stronger directional propagation toward ipsilateral mesial temporal areas than PCC epilepsy (p = 0.022), whereas PCC epilepsy lacked consistent directional connectivity across key regions.

RSC and PCC epilepsy display inherent differences in visuospatial memory performance and ictal network dynamics. The preferential propagation toward ipsilateral mesial temporal structures in RSC epilepsy may represent a potential electrophysiological correlate for distinguishing posterior cingulate epilepsy subtypes.