Localizing epileptogenic zones with high-frequency oscillations and directed connectivity

Purpose: Precise localization of the epileptogenic zone (EZ) is essential for epilepsy surgery. Existing methods often fail to detect slow onset patterns or similar neural activities presented in the recorded signals. To address this issue, we propose a new measure to quantify epileptogenicity, i.e., the connectivity high-frequency epileptogenicity index (cHFEI). Methods: The cHFEI method combines directed connectivity and high-frequency oscillations (HFOs) to measure the epileptogenicity of regions involved in a brain network. By applying this method to stereoelectroencephalography (SEEG) recordings of 49 seizures in 20 patients, we calculated the accuracy, sensitivity, and precision with a visually identified epileptogenic zone as a reference. The performance was evaluated by the confusion matrix and the area under the receiver operating characteristic (ROC) curve. Results: Epileptic network estimation based on cHFEI successfully distinguished brain regions involved in seizure onset from the propagation network. Moreover, cHFEI outperformed other existing detection methods in the estimation of EZs in all patients, with an average area under the ROC curve of 0.88 and an accuracy of 0.85. Conclusions: cHFEI can characterize EZ in a robust manner despite various seizure onset patterns and has potential application in epilepsy therapy.

Automated summary

A new measure called connectivity high-frequency epileptogenicity index (cHFEI) is proposed to accurately quantify the epileptogenic zone (EZ) in epilepsy surgery. The cHFEI method combines directed connectivity and high-frequency oscillations (HFOs) to distinguish brain regions involved in seizure onset from the propagation network. It outperforms existing detection methods and shows potential for epilepsy therapy.