Predictors of Early Postoperative Seizures Following STA–MCA Bypass in Adult Moyamoya Angiopathy

Background: Postoperative epileptic seizures are a recognized complication after superficial temporal artery–middle cerebral artery (STA–MCA) bypass for Moyamoya angiopathy (MMA), but their determinants remain incompletely understood. We aimed to identify clinical, radiological, and perioperative factors associated with early postoperative seizures following adult STA–MCA bypass. Methods: We retrospectively analyzed 75 hemispheric revascularization procedures performed in adult MMA patients between 2005 and 2023, with each operated hemisphere treated as an independent analytical unit. The primary outcome was the occurrence of at least one in-hospital postoperative seizure; the primary exposure was cerebral hyperperfusion syndrome. Univariate and multivariable Firth penalized-likelihood logistic regression was used to account for the small sample size and rare outcome. Results: Postoperative seizures occurred in 14 of 75 procedures (18.7%). Hyperperfusion was identified in 6 procedures (8.0%) and showed the strongest univariate association with seizures (OR 10.20), followed by diabetes mellitus (OR 6.05). Right-hemispheric procedures showed a protective effect in the univariate analysis (OR 0.24). In separate multivariate adjusted models, hyperperfusion (OR 10.28) and diabetes mellitus (OR 5.70) remained associated with postoperative seizures (OR 10.28 and OR 5.70, respectively). Pre-existing epilepsy, antiepileptic treatment, and preoperative EEG abnormalities were not associated with seizure risk. Conclusions: Early postoperative seizures after direct STA–MCA bypass in adult MMA were most consistently associated with postoperative cerebral hyperperfusion in our cohort, while pre-existing epilepsy and preoperative EEG abnormalities showed no statistically significant associations. Early recognition of hyperperfusion may support risk-stratified postoperative surveillance and individualized management.