Understanding late-window cerebral vasospasm in aneurysmal subarachnoid hemorrhage

Cerebral vasospasm is a major determinant of neurologic outcome following aneurysmal subarachnoid hemorrhage (aSAH). While vasospasm typically occurs between days 3 and 10 after admission, a subset of patients develop vasospasm beyond this conventional window. The factors contributing to this late-window presentation remain poorly characterized. In this study, we sought to determine the incidence of late-window vasospasm and identify its independent clinical and radiographic predictors.

Patients with cerebral vasospasm identified on transcranial Doppler or CT angiography were selected from a prospectively maintained database of patients with aSAH admitted between 2003 and 2024. Variables associated with late-window vasospasm (occurring > 10 days from symptom onset) at p < 0.05 in univariable analyses were subsequently entered into a multivariable logistic regression model to identify independent predictors.

Among 370 patients with aSAH, 192 (51.9%) were diagnosed with vasospasm (median age 54 years [IQR 46-62]; 123 female). Late-window vasospasm occurred in 27 patients (14.1%). In univariable analysis, female sex, smoking history, surgical aneurysm treatment, Fisher grade, and delayed aneurysm treatment (> 48 h after symptom onset) were significantly associated with late-window vasospasm. After multivariable adjustment, higher Fisher grade (aOR 2.34, 95% CI 1.30-4.24, p = 0.005) and delayed aneurysm treatment (aOR 8.86, 95% CI 2.98-26.36, p < 0.001) remained independent predictors. There were no significant differences in length of stay (24 vs. 20 days, p = 0.051) or poor functional outcome (modified Rankin scale [mRS] ≥ 3) at discharge (63.0% vs. 47.9%, p = 0.146) between patients with and without late-window vasospasm.

Approximately one in seven patients with vasospasm experienced onset beyond 10 days. Higher Fisher grade and delayed aneurysm treatment were independently associated with late-window vasospasm. These findings suggest continued neurovascular surveillance beyond the first 10 days may be important for patients with these risk factors.