Application of Electric Source Imaging for Analysis of Epileptic Seizures

Epilepsy is a chronic neurological disorder originating as a result of hypersynchronous neuronal activity in the brain, characterized by seizures. For the treatment of pharmacoresistant focal epilepsy, surgical resection of epileptogenic zone is required. The source of epileptic hypersynchrony can be single or multiple. Success of the surgery depends upon the accuracy of identification of the epileptic focus and resection of it without inducing potential functional impairment. An inverse solution method to estimate the epileptic focus prior to performing the surgery is developed. The foci of epileptic discharge are localized using the low resolution EEG and MRI acquired from the patient. The MRI is taken by placing markers exactly at the EEG electrode positions, which are then digitized to obtain 3D coordinates. A patient specific surface head model was reconstructed from the MRI using expectation maximization algorithm. The location of the epileptic focus is mapped on the patient’s cortical surface model using weighted minimum norm estimates (WMNE). A pilot study to demonstrate the validity and usefulness of electric source imaging in neurosurgery is carried out. The focus of epileptic discharge was identified by inverse modeling. These results were found to be concordant with the clinical diagnosis and treatment, following which the subject was found to be seizure free.