Prospective observational study: Fast ripple localization delineates the epileptogenic zone.

Area of Science:

• Epilepsy research
• Neurophysiology
• Surgical neurology

Background:

• Pharmacoresistant focal epilepsy presents significant treatment challenges.
• Accurate localization of the epileptogenic zone is crucial for successful surgical intervention.
• Limitations of current neuroimaging in fully delineating the extent of epileptic tissue.

Purpose of the Study:

• To investigate the spatial correlation between interictal high-frequency oscillations (HFOs), specifically fast ripples (FRs), and neuroimaging abnormalities.
• To determine if complete resection of prospectively identified interictal FRs correlates with post-surgical seizure freedom.
• To assess the utility of interictal FRs in localizing epileptogenic zones beyond conventional imaging.

Main Methods:

• Prospective analysis of interictal fast ripples (FRs: 250-500 Hz) in 19 children with pharmacoresistant focal epilepsy.
• Electrocorticography (ECoG) recordings analyzed for FRs during slow-wave sleep.
• Delineation of FRs, MRI, and FDG-PET on patient-specific 3D brain models.

Main Results:

• Interictal FRs were detected in 18 out of 19 patients.
• In 72% of patients, FRs extended beyond the visible neuroimaging abnormalities.
• Complete resection of cortical sites with FRs correlated significantly with longer seizure freedom (p < 0.01), outperforming resection of neuroimaging abnormalities (p = 0.43).

Conclusions:

• Prospective visual analysis of interictal FRs is a feasible method for accurately localizing epileptogenic zones.
• The epileptogenic region's topological extent can surpass what is detectable by multimodal neuroimaging.
• Resection of FR-identified areas, not just visible abnormalities, is key for improved surgical outcomes in epilepsy.