Objective:

NA

Background:

Small sharp spikes (SSS) are brief, low-amplitude temporal transients with uncertain clinical relevance. Emerging evidence suggests that SSS frequently occur in patients with MTLE and may be associated with epileptiform discharges; however, their diagnostic value and the morphological characteristics indicative of pathogenicity are not well established. We investigated whether quantitatively defined SSS detected by magnetoencephalography (MEG) can assist in SOZ localization in drug-resistant MTLE and how these findings relate to EEG, MRI, and stereo-EEG (sEEG) data.

Design/Methods:

We retrospectively reviewed consecutive patients with drug-resistant MTLE who underwent comprehensive pre-surgical evaluation at the University of Florida. The evaluation included MEG with simultaneous scalp EEG, routine or long-term EEG, structural MRI, and sEEG when clinically indicated. SSS were identified on MEG and EEG recordings and quantified using standardized morphological criteria, including amplitude, duration, and waveform characteristics.

Results:

Across our cohort, MEG identified SSS that were often not apparent on simultaneous scalp EEG. Source localization of MEG-detected SSS consistently clustered within ipsilateral mesial temporal structures on co-registered MRI. The frequency of SSS events was quantified, and spikes confirmed as likely epileptiform discharges on surface or stereo-EEG (sEEG) were characterized. Quantitative morphological analysis further distinguished MEG-SSS arising from mesial temporal sources from benign-appearing, broadly distributed variants observed on scalp EEG.

Conclusions:

Integration of MEG, EEG, and MRI shows that SSS observed in MEG often localize to abnormal mesial temporal lobe pathology with electrographic correlation. Quantitative spike analysis in MEG provides a new window into the utilization of MEG in pre-surgical evaluation and incorporating MEG-based SSS analysis may enhance diagnostic confidence and guide invasive monitoring and surgical planning, particularly in non-lateralizing or bilateral cases.