Modulation of EEG Background Rhythms in Sturge-Weber Syndrome: Impact of Surgical Timing on the Unaffected Hemisphere

Epilepsy surgery improves seizure outcomes in Sturge-Weber syndrome (SWS), yet the electrophysiological patterns of postoperative recovery remain poorly characterized. Previous studies suggest that early intervention may yield distinct clinical trajectories, but the associated changes in EEG background activity have not been systematically investigated.

To investigate whether age of surgery influences the postoperative modulation of EEG background rhythms in children with unilateral SWS, and to evaluate the utility of preoperative EEG asymmetry for lateralizing the epileptogenic hemisphere.

Retrospective cohort study.

We analyzed children with unilateral SWS who underwent epilepsy surgery, stratified by age at intervention (<2 vs. ≥2 years). Pre- and postoperative scalp EEGs were visually assessed to quantify posterior dominant alpha frequency and slow-wave (delta and theta bands) activity separately in the affected and unaffected hemispheres (AH, UH). Preoperative lateralization accuracy was also evaluated for both frequency bands.

A total of 99 patients were included. Seizure freedom rates were comparable between age groups. However, younger patients exhibited a significantly greater postoperative increase in alpha frequency, particularly in the UH (20 ± 20% vs. 4 ± 10%, P < 0.001). This effect was consistent across both focal resection (17±12% vs. 1 ± 8%, P < 0.001) and hemispheric surgery (22 ± 22% vs. 7 ± 11%, P = 0.006). In contrast, slow-wave modulation did not differ by age. Preoperative alpha asymmetry correctly lateralized the surgical hemisphere in 86.9% of cases (sensitivity 85.7%, specificity 88.0%, κ = 0.74), outperforming slow-wave asymmetry (accuracy 66.7%, κ = 0.33).

Early epilepsy surgery in SWS is associated with enhanced postoperative modulation of alpha frequency in the UH, possibly reflecting greater neuroplastic capacity during early development. Preoperative alpha asymmetry offers robust lateralizing value. These findings support the clinical utility of background EEG analysis in surgical planning and postoperative monitoring.