title: Subarachnoid hemorrhage: beyond aneurysms.
abstract: OBJECTIVE
  Spontaneous subarachnoid hemorrhage (SAH) typically prompts a search for an underlying ruptured saccular aneurysm, which is the most common nontraumatic cause. Depending on the clinical presentation and pattern of SAH, the differential diagnosis may include a diverse group of causes other than aneurysm rupture.
  
  
  CONCLUSIONS
  For the purposes of this review, we classify SAH into three main patterns, defined by the distribution of blood on unenhanced CT: diffuse, perimesencephalic, and convexal. The epicenter of the hemorrhage further refines the differential diagnosis and guides subsequent imaging. Additionally, we review multiple clinical conditions that can simulate the appearance of SAH on CT or MRI, an imaging artifact known as pseudo-SAH.
authors.affiliation: 1 All authors: Department of Radiology, University of Washington, Box 357115, 1959 NE Pacific St, NW011, Seattle, WA 98195-7115.
authors.forename: Carrie P
authors.initials: CP
authors.lastname: Marder
authors.forename: Vinod
authors.initials: V
authors.lastname: Narla
authors.forename: James R
authors.initials: JR
authors.lastname: Fink
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: Tozer Fink
mesh_terms: D017542:Aneurysm, Ruptured / Q000150:complications / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography; D003937:Diagnosis, Differential; D006801:Humans; D002532:Intracranial Aneurysm / Q000150:complications / Q000000981:diagnostic imaging*; D012422:Rupture, Spontaneous; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging* / Q000209:etiology; D014057:Tomography, X-Ray Computed / Q000379:methods*