Purpose: The purpose of this work was to find an objective and quantitative method for epileptic foci lateralization that may aid and support the decision made by the usually chosen lateralizing criteria.
Methods: A frequency-derived causal analysis method, full frequency adaptive directed transfer function, was applied to the interictal scalp EEG data collected from 2 groups of total 30 epileptic patients. Group A included 15 refractory epileptic patients who had undergone an epileptic surgery; group B consisted of 15 outpatient epileptic patients who had a seizure type of generalized tonic-clonic seizure. All patients had no abnormalities detected in their routine brain MRI examinations. The methodology that leads to the lateralization is based on several processing steps: interictal spikes selection, full frequency adaptive directed transfer function analysis, significant causal connections extraction, and then lateralization.
Results: Ninety-six of 104 spikes' sources lateralized by full frequency adaptive directed transfer function were consistent with their corresponding surgery side in group A, with the accuracy of 92.31%. Ninety-seven of 101 spikes' sources were lateralized correctly in group B, according to technicians' judgments from ictal scalp video-EEG recordings, with the accuracy of 96.04%.
Conclusions: The results demonstrated the feasibility of correctly lateralizing the epileptic foci by using full frequency adaptive directed transfer function to scalp EEG interictal spike activity.