Distinguishing epileptogenic hippocampus in nodular heterotopia patients using functional connectivity.

OBJECTIVE

To investigate the epileptogenicity of the hippocampus in patients with PNH using functional connectivity (FC).

METHODS

PNH patients with intracranial electrodes implanted in both heterotopic nodules (HNs) and the hippocampus, and who achieved seizure freedom postoperatively, were retrospectively enrolled.Hippocampal epileptogenicity was determined based on the surgical outcomes after hippocampus coagulation or not. The epileptogenicity index (EI) was calculated for both HNs and hippocampal channels. Interchannel FC during the interictal state (cortico-cortical evoked potential, CCEP) and ictal state (h2 coefficient) was calculated and compared. A logistic regression model was developed using significant ictal FC biomarkers to predict hippocampal epileptogenicity.

RESULTS

A total of 8 patients were enrolled, with 6 undergoing CCEP. No significant EI differ-ences were observed between HNs and hippocampal channels. In patients with hippocampal epileptogenicity, connectivity from the hippocampus to HNs was stronger during both interictal and ictal states compared to the reverse. This trend was not seen in patients without hippocampal epileptogenicity. A logistic regression model incorporating ictal FC differences distinguished hippocampal epileptogenicity with an ac-curacy of 0.79 and an AUC of 0.81.

CONCLUSION

A classification model based on ictal FC effectively differentiates hippocampal epileptogenicity in PNH patients and may serve as a valuable tool for guiding surgical decisions.