Change in Resting-State functional MRI Connectivity to Measure Individual Response to Epilepsy Surgery

Objective

This study evaluates fractional power spectrum contribution (fPSC), a biomarker derived from resting-state functional MRI (rs-fMRI), as an indicator of epileptogenic network activity in drug-resistant epilepsy (DRE) patients undergoing surgery. We aimed to assess pre-to post-operative changes in fPSC and their correlation with seizure outcomes.

Methods

A retrospective cohort of 56 pediatric DRE patients with pre- and post-operative rs-fMRI were evaluated. Independent component analysis (ICA) was applied to identify resting-state networks (RSNs). Each ICA RSN’s power spectrum within the range of 0.06–0.25 Hz was quantified by fPSC. The change in this fPSC was compared pre- and post-operatively using paired t-tests. Multivariate analyses including correlations with clinical outcomes were evaluated by linear mixed effects models and ANOVA.

Results

Among the 56 patients, 80.4% demonstrated greater than 50% seizure reduction post-surgery, with 64.3% achieving seizure freedom. fPSC significantly decreased after surgery (t=3.0, p=0.005), indicating a reduction in epileptogenic network activity. The mixed effects model, controlling for covariates, also showed a significant effect of post-surgical scan on fPSC reduction (χ ^² =8.4, df=1, p=0.004). However, there was insufficient evidence to establish an association between changes in fPSC and clinical improvement score (p=0.16) or seizure frequency (p=0.49).

Conclusion

The observed reduction in fPSC post-surgery highlights its potential as a biomarker of atypical network activity in epilepsy, offering a network-specific, whole-brain approach independent of anatomical coordinates. However, its lack of correlation with clinical outcomes underscores the need for further refinement and validation to establish fPSC as a reliable measure of epileptogenic burden.

HIGHLIGHTS

• fPSC analysis using rs-fMRI detects a moderate treatment effect of epilepsy surgery, independent of relative network volume changes.

• fPSC analysis provides a method to quantify whole-brain network dysfunction in epilepsy without the need for a seizure onset zone identification-hypothesis.

• A trend towards direct correlation is observed between fPSC post-operative change and seizure outcomes in epilepsy surgery.