Postictal electroencephalographic suppression in generalized tonic-clonic seizures: clinical correlates and predictive factors from a cross-sectional observational study

• Gradual clonic termination was the strongest independent PGES predictor. • Secondary seizures linked to prolonged PGES and widespread cortical suppression. • Higher BMI linked to prolonged PGES and postictal respiratory risk. • PGES may help identify patients at elevated SUDEP risk. This study aimed to identify clinical and seizure-related factors associated with the occurrence and duration of PGES in patients with GTCs. A cross-sectional observational study was conducted on 142 patients admitted to a long-term video-EEG monitoring unit between March 2023 and 2024. Demographic, clinical, and electrographic data were extracted retrospectively. PGES was defined as generalized EEG suppression <10 µV within 30 s post-seizure. Statistical analyses included univariate comparisons and multivariate logistic regression to identify independent predictors. PGES was observed in 71.1% of patients. Gradual termination of the clonic phase was the strongest independent predictor of PGES (OR = 2.32, 95% CI: 1.02–5.89, p = 0.045). Patients with PGES had significantly higher body mass index (BMI) and longer seizure durations. Focal to bilateral tonic–clonic seizures were significantly associated with prolonged PGES (>30 s). No significant differences were found in heart rate variability or postictal paresis. PGES is a frequent postictal phenomenon in patients with GTCs and is associated with specific seizure dynamics and systemic factors. Gradual clonic phase termination, longer seizure duration, and elevated BMI may serve as clinical markers for PGES. These findings highlight the importance of individualized postictal monitoring and may contribute to improved SUDEP risk stratification and targeted care strategies.