To compare predictors of seizure in aneurysmal subarachnoid hemorrhage (aSAH) and angiogram-negative non-perimesencephalic SAH (an-NPSAH) groups.

Although predictors of seizure in aSAH patients have been explored, less is known for an-NPSAH patients. We sought to compare the predictors of seizure in these cohorts.

We conducted a retrospective study on patients admitted to an academic center from July 2016 to July 2023, categorizing patients into aSAH or an-NPSAH groups based on imaging. We used binary regression analysis to assess the association between predictors of seizures and outcomes.

We reviewed 473 cases (63% female): 79 an-NPSAH and 394 aSAH. Patients in an-NPSAH group were older (mean age 61.9 years [SD 15.9] vs 56.7 [SD 13.4]). Clinical seizure at presentation or during hospital admission was seen in 8 an-NPSAH and 48 aSAH patients (10% vs 12%; p=0.6). EEG (80% spot, 20% long-term monitoring) was performed in 259 patients (55%): epileptic features were captured in 12 an-NPSAH and 52 SAH patients (15% vs. 13%; p=0.63). Both groups had similar rates of clinical and/or electrographic seizures (25.3% vs 25%; p=0.99). Predictors of aSAH seizure included Hunt and Hess grade (OR 1.25 per grade increase, 95% 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) and cerebral infarct at presentation or during admission (OR 3.64, 95% CI 2.13-6.23; p<0.001). Neither intracerebral hemorrhage nor aneurysm securement modality was associated with seizure. None of these factors were associated with seizure in an-NPSAH.

Clinical or electrographic seizures are seen with similar rates in both groups. However, the predictors of seizures appear to be different. Larger prospective studies are needed to identify predictors of seizure in an-NPSAH patients.