Cortical abnormalities in epilepsy revealed by local EEG synchrony

Area of Science:

• Neuroscience
• Epileptology
• Clinical Electrophysiology

Background:

• Abnormally strong functional connectivity between cortical areas is implicated in the pathogenesis of partial epilepsy.
• Interictal electroencephalography (EEG) may reveal these linkages beyond typical epileptiform discharges.

Purpose of the Study:

• To investigate if heightened functional linkage, termed "hypersynchrony," is detectable in interictal intracranial EEG (ICEEG) in patients with partial epilepsy.
• To determine if hypersynchrony patterns correlate with seizure localization and can serve as a marker for epileptogenic cortex.

Main Methods:

• Analysis of interictal ICEEG data from subdural grids in nine patients with medically intractable partial epilepsy.
• Quantification of interelectrode synchrony using the mean phase coherence algorithm to identify areas of local hypersynchrony.

Main Results:

• Identification of distinct areas of elevated local synchrony (hypersynchrony) with persistent, patient-specific spatiotemporal characteristics.
• Development of cortical surface maps of local synchrony, revealing information not apparent on visual EEG or imaging.

Conclusions:

• Local hypersynchrony detected via ICEEG may serve as a potential biomarker for epileptogenic cortex in partial epilepsy.
• This quantitative analysis of synchrony could enhance the interpretation of ICEEG data for clinical localization of seizures.