Acute Convexity Subarachnoid Hemorrhage Related to Cerebral Amyloid Angiopathy: Clinicoradiological Features and Outcome

Background: The specificities of acute convexity subarachnoid hemorrhage (cSAH) related to cerebral amyloid angiopathy (CAA) and its evolution are not well known. We aimed to describe the clinicoradiological pattern, the magnetic resonance imaging (MRI) evolution, and the risk of recurrent bleeding in such patients. Methods: Among consecutive patients with an acute nontraumatic cSAH, subjects with available MRI who meet the modified Boston criteria for probable CAA were included. Review of medical records, MRI findings, and follow-up data was performed. Results: Twenty-three patients (14 women; mean age +/- standard deviation: 75.9 +/- 7.3 years) were included. cSAH was revealed by transient focal neurological episodes (TFNEs) in 18 of 23 (78.3%) patients. In all patients, acute cSAH appeared as a sulcal fluid-attenuated inversion recovery hyperintensity and GRE T2 hypointensity. Cortical superficial siderosis and cortical microbleeds, respectively, were observed in 21 (91.3%) and 20 (86.9%) patients. Twenty patients (87%) had available follow-up data with a mean duration of 29.8 +/- 20.2 months. Recurrent TFNEs occurred in 40% of patients. Acute cSAH evolved into cortical superficial siderosis in all patients. New subarachnoid bleedings defined by recurrent acute cSAH (n = 8) or extension of siderosis (n = 14) were detected in 83.3% of the patients. Lobar intracerebral hemorrhage (ICH) occurred in 7 patients (35%). Conclusion: CAA-related cSAH has a specific pattern defined by a high prevalence of TFNEs and cortical superficial siderosis, with a high risk of recurrent bleeding, either cSAH or lobar ICH. The systematic evolution from cSAH to focal cortical superficial siderosis reveals data on siderosis physiopathology.