Comparison of Risk Factors for Early Seizures Between Angiogram-Negative and Aneurysmal Subarachnoid Hemorrhage

Background: Early-onset seizures are common in aneurysmal subarachnoid hemorrhage (aSAH), with risk factors that have been explored. However, early-onset seizures in patients with angiogram-negative nonperimesencephalic SAH (an-SAH) are less understood. We sought to compare the incidence and risk factors of early-onset seizures between these groups. Methods: We conducted a retrospective study of a cohort of consecutive patients admitted to an academic center between July 2016 and July 2023. Patients were categorized into aSAH or an-SAH based on imaging findings. Clinical data and electroencephalogram findings were retrieved and analyzed. Multivariable logistic regression analysis was used to determine risk factors for clinical or electrographic seizures, as well as other epileptic features. Results: We included 473 patients (63% female) in the final analysis, of whom 79 had an-SAH and 394 had aSAH. Patients with an-SAH were older (mean age 61.9 years [standard deviation 15.9] vs. 56.7 [standard deviation 13.4]; p = 0.02). The rate of clinical or electrographic seizures was similar between the two groups (13% in aSAH vs. 11% in an-SAH; p = 0.62). Highly epileptic features (electrographic seizures, ictal-interictal continuum, and periodic epileptic discharges) occurred more frequently in the aSAH group compared with the an-SAH group, although this difference was not significant (15% vs. 8%; p = 0.09). Risk factors for seizures in aSAH were Hunt and Hess grade (odds ratio [OR] 1.25 per grade increase, 95% confidence interval [CI] 1.05-1.49; p = 0.011), modified Fisher score (OR 1.64 per point increase, 95% CI 1.25-2.15; p < 0.001), cerebral infarct (OR 3.64, 95% CI 2.13-6.23; p < 0.001), and intracerebral hemorrhage (OR 10, 95% CI 1.35-76.9; p = 0.017). However, none of these factors were associated with seizures in an-SAH. Conclusions: Early-onset seizures occur at similar rates in patients with an-SAH and aSAH. However, seizure risk factors appear to differ between these groups. Larger prospective studies are needed to identify predictors of seizures in patients with an-SAH.