Mapping epileptogenic brain using a unified spatial-temporal-spectral source imaging framework

Area of Science:

• Neuroscience
• Medical Imaging
• Epileptology

Background:

• Noninvasive electrophysiological source imaging (ESI) is crucial for localizing brain activity in focal drug-resistant epilepsy (fDRE).
• Various scalp electroencephalography (EEG) biomarkers like spikes and high-frequency oscillations (HFOs) are used to estimate the epileptogenic zone (EZ), but their comparative precision is not well understood.
• Distinct processing pipelines are often required for different biomarkers, limiting quantitative comparisons.

Purpose of the Study:

• To develop a unified spatial-temporal-spectral imaging (STSI) framework for precise source imaging of epilepsy biomarkers.
• To quantitatively evaluate and compare the source-imaging precision of different EEG biomarkers (spikes, HFOs, seizures) in fDRE patients.
• To establish a more accurate method for presurgical planning in fDRE.

Main Methods:

• Developed and applied a novel spatial-temporal-spectral imaging (STSI) framework.
• Analyzed 2,081 individual epilepsy events (spikes, HFOs, seizures) from 42 fDRE patients.
• Compared source imaging results against clinical ground truth, including surgical resection outcomes and intracranial EEG-defined seizure onset zones.

Main Results:

• The STSI framework enabled quantitative comparisons of localization errors for various biomarkers.
• Seizures showed the lowest localization error (6.67 mm), followed by HFOs overlapping with spikes (pHFO, 8.73 mm) and HFO-riding spikes (pSpike, 10.28 mm).
• General spikes (aSpike, 19.59 mm) and general HFOs (aHFO, 36.53 mm) exhibited larger localization errors in seizure-free patients.

Conclusions:

• HFOs overlapping with spikes represent the most spatially accurate interictal biomarker for mapping the epileptogenic zone.
• The STSI framework provides a unified approach for analyzing epileptic biomarkers, enhancing presurgical planning for fDRE.
• The STSI framework has broader potential applications in cognitive neuroscience and clinical management of neurological disorders.