Source localization of ictal epileptic activity based on high-density scalp EEG data

Area of Science:

• Neuroscience
• Epileptology
• Medical Imaging

Background:

• Electrical source imaging (ESI) is a standard method for identifying the epileptic focus in drug-resistant focal epilepsy.
• Current applications of ESI primarily utilize interictal events, with growing interest in the potential of ictal ESI.

Purpose of the Study:

• To evaluate the diagnostic accuracy of ictal ESI using high-density electroencephalography (EEG) for localizing the epileptic focus.
• To assess the utility of ictal ESI in presurgical evaluation for focal epilepsy.

Main Methods:

• Ictal ESI was performed on 14 patients with focal epilepsy undergoing presurgical evaluation using high-density EEG (128 or 256 electrodes).
• Artifact-free EEG data at seizure onset were analyzed, with predominant ictal rhythms filtered and ESI computed using individual head models.
• Results were validated against surgical resection areas and postoperative outcomes.

Main Results:

• Ictal ESI correctly localized the seizure-onset zone in the resection area in 5 out of 6 patients who became seizure-free post-surgery.
• Interictal and ictal ESI results were concordant in 93% of patients (9/14 fully concordant, 4/14 partially concordant).
• Discrepant localization findings between interictal and ictal ESI occurred in only 7% of cases (1/14).

Conclusions:

• Ictal ESI demonstrates significant potential as a precise localization technique for the epileptic focus in focal epilepsy.
• The high concordance between ictal and interictal ESI suggests its reliability in presurgical epilepsy assessment.