Abstract TP534: Comparing the Outcomes of Patients With Idiopathic Subarachnoid Hemorrhage by Three Distinct Perimesencephalic Bleed Patterns

Abstract

Introduction: Most studies on idiopathic subarachnoid hemorrhage (SAH) focus on comparing perimesencephalic bleeds (PSAHs) to aneurysmal SAHs. We divided PSAHs into three distinct bleed groups and compared clinical courses and outcomes. Methods: We included adult patients (≥18) with angiography-negative, non-traumatic SAH treated at a comprehensive stroke center (1/2015-5/2018). We excluded patients with known etiologies and convexity bleeds (N=41). Patients were categorized by bleed location on CTA: Peri-1: focal prepontine; Peri-2: pan-suprasellar cisterns; Peri-3: pan-suprasellar cisterns + sylvian fissures + intraventricular extension. Outcomes were cerebral ischemia (CI), hydrocephalus and severity, neuro critical care length of stay (NCCU LOS), and hospital LOS. Results: Of the 43 patients included in the study, 37% were Peri-1, 28% were Peri-2, and 35% were Peri-3. A majority were male (67%), with a median (IQR) age of 57 (44-63), and often presented with a headache (93%), nausea (72%), and a Hunt and Hess score of 1-3 (93%). Patients presenting with lethargy (6% vs. 17% vs. 67% p=0.006) and a modified Fisher score of 3 vs. 4 (100% vs. 92% vs. 33% p<0.001) were significantly different between groups in Peri-1-3, respectively. A history of hypertension (19% vs. 25% vs. 60% p=0.04) and mean (SD) days on nimodipine treatment (9.1(4.8) vs. 11.9(7.3) vs. 15.1(5.9), p=0.03) were significantly different between groups. Six (14%) patients had severe hydrocephalus and eight (19%) had CI. Median NCCU and hospital LOS, and proportion with hydrocephalus, were significantly different between groups. (Table 1). There were no other significant differences in outcomes between groups. Conclusions: Our study suggests that patients with the best outcomes were those in Peri-1, followed by Peri-2, and then Peri-3. Because there are no clear risk factors for PSAH, understanding differences by bleed patterns may help tailor better treatment strategies for this population.