The Spectrum of Nontraumatic Convexity Subarachnoid Hemorrhage.

BACKGROUND: Nontraumatic convexity subarachnoid hemorrhage (cSAH) is a nonaneurysmal variant that is associated with diverse etiologies. METHODS: With IRB approval, we retrospectively reviewed consecutive nontraumatic cSAH from July 1, 2006 to July 1, 2016. Data were abstracted on demographics, medical history, neuroimaging, etiology, and clinical presentation. RESULTS: We identified 94 cases of cSAH. The cases were classified according to the following etiologies: reversible cerebral vasoconstriction syndrome (RCVS) 17 (18%), cerebral amyloid angiopathy (CAA) 15 (16%), posterior reversible encephalopathy syndrome 16 (17%), cerebral venous thrombosis 10 (11%), large artery occlusion 7 (7%), endocarditis 6 (6%), and cryptogenic 25 (27%). Early rebleeding occurred in 9 (10%) patients. Time from initial imaging to CT rebleeding was 40 hours (range, 5-74). CAA was associated with the highest mean age at 75.8 and RCVS the lowest at 47.6 years (P< .0001). Among patients with RCVS, initial vascular imaging was negative in 6 (35%), and repeat imaging documented vasoconstriction at a mean delay of 5 days (range, 3-16). CONCLUSION: There were significant differences among the subgroups in cSAH, with CAA presenting as older men with transient neurological deficits, and RCVS presenting as younger women with thunderclap headache. Rebleeding was seen in 10% of cSAH patients. One-third of RCVS patients with cSAH required repeat vascular imaging to diagnose vasoconstriction.