High-resolution source imaging in mesiotemporal lobe epilepsy: a comparison between MEG and simultaneous EEG.

Area of Science:

• Neurology
• Medical Imaging
• Epileptology

Background:

• Non-lesional mesiotemporal lobe epilepsy (MTLE) is the most common epilepsy type requiring surgery.
• Accurate localization of epileptic foci is crucial for surgical planning in MTLE.
• Magnetic source imaging (MSI) is proposed as a tool for precise epileptic focus localization.

Purpose of the Study:

• To compare whole-head magnetoencephalography (MEG) with high-resolution electroencephalography (EEG) for source identification in MTLE.
• To evaluate the accuracy of MSI in localizing epileptic foci in non-lesional MTLE.
• To assess the correlation of MSI findings with intraoperative electrocorticography (ECoG).

Main Methods:

• Simultaneous 151-channel CTF MEG and 64-channel EEG recordings were performed in 19 patients with unilateral, non-lesional MTLE.
• Spike detection and selection were done by three independent observers with consensus averaging.
• Equivalent current dipole (ECD) modeling was used to localize sources, with results compared to intraoperative ECoG.

Main Results:

• Spike detection rates were 32% for MEG and 42% for EEG; no patient had MEG-only spikes.
• ECD modeling localized sources to the temporal lobe in 4/5 MEG and 3/8 EEG recordings.
• MEG sources were more superficial, EEG sources deeper; basal temporal lobe coverage by MEG was insufficient.

Conclusions:

• MSI is currently unlikely to alter surgical management for MTLE due to low spike yield and partial correlation with ECoG.
• Insufficient temporal lobe coverage by whole-head MEG helmets limits its clinical utility.
• Further advancements in MSI technology are needed for improved epileptic focus localization in MTLE.