Normative high-frequency oscillation phase-amplitude coupling and effective connectivity under sevoflurane

Area of Science:

• Neuroscience
• Epilepsy Research
• Anesthesiology

Background:

• Paediatric drug-resistant focal epilepsy surgery requires invasive intracranial electroencephalography (iEEG) for accurate epileptogenic zone localization.
• Current diagnostic methods involve multiple surgeries and prolonged inpatient evaluations, highlighting a need for less burdensome, objective epilepsy biomarkers.
• Preliminary studies showed sevoflurane anesthesia could activate phase-amplitude coupling and effective connectivity biomarkers, potentially correlating with seizure freedom.

Purpose of the Study:

• To elucidate the normative distribution and propagation pathways of sevoflurane-activated electrocorticography (ECoG) biomarkers across different anesthetic stages.
• To determine if sevoflurane-enhanced ECoG biomarker values can intraoperatively localize epileptogenic sites.
• To establish baseline understanding before prospective use of these biomarkers for guiding epilepsy surgery.

Main Methods:

• ECoG was recorded from 19 paediatric epilepsy patients (ages 4-18) under isoflurane baseline, increasing sevoflurane concentrations, and slow-wave sleep.
• Phase-amplitude coupling (delta-high frequency) and high-frequency activity-based effective connectivity were analyzed.
• Normative electrode sites were mapped, white matter pathways traced using dynamic tractography, and biomarker values correlated with epileptogenicity.

Main Results:

• Normative ECoG biomarkers increased with sevoflurane concentration, particularly in frontal and parietal lobes (p < 0.05).
• Callosal and superior longitudinal fasciculus pathways connected regions with elevated biomarkers.
• Higher biomarker values at 3-4 vol% sevoflurane significantly characterized epileptogenicity and seizure-onset zones (p < 0.05).

Conclusions:

• This study clarifies the normative distribution and propagation pathways of sevoflurane-enhanced ECoG biomarkers.
• Sevoflurane-activated biomarkers, especially at specific concentrations, show potential for intraoperative localization of epileptogenic sites.
• Further validation in larger cohorts is needed to confirm predictive value for postoperative seizure outcomes and clinical utility.