The overall incidence of true aneurysms in patients with angiogram-negative SAH is low (2.9%). Initial bleeding pattern strongly correlates with diagnostic yield and clinical outcome. Diffuse bleeding pattern is associated with significantly higher diagnostic yield, more in-hospital complications, and worse clinical outcome. Patients with initial imaging characteristics other than diffuse pattern SAH developed few disease related complications, with the majority of in-hospital adverse events treatment related 1).
Standard magnetic resonance imaging (MRI) rarely identifies the cause of hemorrhage in patients with an angiogram-negative, non perimesencephalic subarachnoid hemorrhage (SAH). Yet up to 10 % of these patients have recurrent hemorrhage
Vessel wall-MRI showed abnormalities in seven patients with angiogram-negative SAH. These findings did not alter patient management, but the findings may be useful for other physicians who choose to perform vessel wall-MRI in this patient population 2).
Low complication rate, especially in the p-SAH group 3).