Aneurysmal versus “Benign” Perimesencephalic Subarachnoid Hemorrhage

Abstract

ABSTRACTIntroductionThe rate of underlying ruptured aneurysm, complications, and outcomes in “benign” perimesencephalic subarachnoid hemorrhage (PMSAH) are not well known and underreported.MethodsRetrospective analysis of patients with PMSAH from a large tertiary care center (2007-2023). Clinical and imaging data were studied.ResultsEighty-one patients were included with mean age of 55.5 ± 10.3 years. Median (IQR) Hunt and Hess grade was 2 (1-2), and modified Fisher grade was 3 (1-3). An underlying ruptured aneurysm was diagnosed in 5 patients (6.2%). The most common complication was vasospasm in 25 patients (31%) with a significantly higher rate of symptomatic vasospasm among patients with underlying aneurysm (40% vs 2.6%; P=0.01). The median (IQR) time of vasospasm detection was 7 (8-9) days. The majority of vasospasm cases (84%) were asymptomatic, which was not associated with poor outcomes (OR= 0.95, [0.22–4.1],P=0.9) compared to the asymptomatic vasospasm (OR= 8.6, [1.06-69.88],P= 0.04). Hydrocephalus occurred in 10% of patients within one day, at higher rate in the aneurysmal group (40% vs 8%; P=0.07). A total of 88% of patients had a favorable functional outcome (mRS 0-2) at discharge, but at a significantly higher rate in non-aneurysmal patients (91% vs 40%; P=0.01). An underlying aneurysm and hydrocephalus were associated with poor functional status (OR= 14.7, [2.1–104],P=0.007, and OR= 22.6, [4.2–123.5],P<0.001), respectively.Conclusion“Benign” PMSAH pattern was associated with a ruptured aneurysm in 6.2% of patients, which highlights the critical value of conventional cerebral angiogram in the workup. Expectedly, an underlying aneurysm was associated with higher rates of symptomatic vasospasm, hydrocephalus, and lower rates of good clinical outcome. Aneurysm and hydrocephalus were independently associated with poorer outcomes, however, these were detected very early during hospitalization. Vasospasm alone was not associated with poor outcomes. Our findings suggest that non-aneurysmal PMSAH patients can safely be managed with less strict monitoring and a shorter hospital stay.