Interictal and ictal source localization for epilepsy surgery using high-density EEG with MEG: a prospective...

Area of Science:

• Neuroscience
• Clinical Neurology
• Medical Imaging

Background:

• Drug-resistant focal epilepsy poses significant clinical challenges, with underutilization of surgical interventions.
• Accurate localization of the epileptogenic zone is crucial, especially in non-lesional or extensively lesional cases where MRI is inconclusive.
• Existing non-invasive techniques require improvement for precise interictal and ictal localization before seizure propagation.

Purpose of the Study:

• To evaluate the efficacy of synchronized high-density EEG (HDEEG) and magnetoencephalography (MEG) for localizing the epileptogenic zone in drug-resistant focal epilepsy.
• To determine the optimal phase of interictal and ictal discharges for accurate source localization.
• To compare the performance of independent HDEEG source localization (ESL) and MEG source localization (MSL) versus combined assessment (EMSL).

Main Methods:

• Synchronized HDEEG-MEG acquisition in 13 patients with drug-resistant focal epilepsy.
• Application of source localization techniques to interictal epileptiform discharges (IEDs) and ictal discharges at early, mid, and late phases.
• Independent and combined analysis of HDEEG and MEG data, with comparison to intracranial EEG and surgical outcomes (Engel scores).

Main Results:

• HDEEG and MEG detected epileptogenic zone sources more accurately at the earliest resolvable discharge phase.
• Independent assessment of HDEEG and MEG signals outperformed combined analysis (EMSL).
• MEG successfully detected baso-mesial temporal lobe sources; ESL was superior for ictal-surgical resection, while MSL excelled for IED-intracranial EEG.

Conclusions:

• The earliest phase of HDEEG and MEG discharges provides the most accurate localization of the epileptogenic zone.
• Independent analysis of HDEEG and MEG data is recommended over combined approaches for improved accuracy.
• These findings challenge current practices and suggest a refined approach to non-invasive epilepsy localization, potentially reducing reliance on invasive monitoring.