Dynamic Interplay Between Wake Slow Waves and Epileptiform Discharges in the Epileptogenic Zone

Area of Science:

• Neuroscience
• Epileptology
• Biomarker Discovery

Background:

• Epilepsy surgery outcomes are often suboptimal, necessitating novel biomarkers for the epileptogenic zone (EZ).
• Local wake slow waves (LoWS) have been identified as potential regulators of network excitability, interacting with interictal epileptiform discharges (IEDs).
• The interaction between LoWS and IEDs requires further investigation for its association with surgical success.

Purpose of the Study:

• To investigate whether the interaction between LoWS and IEDs is associated with surgical outcomes in patients with intractable focal epilepsy.
• To determine if the temporal dynamics of LoWS and IEDs can serve as biomarkers for delineating the EZ.
• To explore the potential of this interaction as a prognostic biomarker in epilepsy surgery.

Main Methods:

• Retrospective analysis of intracranial recordings from 55 patients with intractable focal epilepsy who underwent epilepsy surgery.
• Utilized linear mixed models to assess the incidence and interaction of IEDs and LoWS in relation to surgical success.
• Employed classification analyses to evaluate the accuracy of the IED-LoWS interaction as a biomarker for the EZ.

Main Results:

• Neither the rate of IEDs nor LoWS in resected versus non-resected areas differed significantly across surgical outcomes.
• The temporal delay from IED to subsequent LoWS, but not the reverse, was significantly associated with surgical outcomes, with shorter delays observed within the EZ.
• Classification analyses achieved 63% accuracy in identifying the EZ based on the IED-LoWS temporal interaction, indicating its potential utility.

Conclusions:

• The temporal proximity of LoWS to preceding IEDs in resected cortical areas is linked to epilepsy surgery outcomes.
• This finding suggests that the IED-LoWS temporal relationship may reflect homeostatic regulation of network excitability within the EZ.
• The IED-LoWS temporal index shows promise as an additional prognostic biomarker for enhancing epilepsy surgery.