title: Subarachnoid hemorrhage without detectable aneurysm. A review of the causes.
abstract: BACKGROUND
  In 15% to 20% of patients with a spontaneous subarachnoid hemorrhage, no aneurysm is found on the first angiogram. This review emphasizes that this group of patients is in fact heterogeneous and describes the clinical features, pattern of hemorrhage on early computed tomographic (CT) scan, prognosis, and proposed management in the several and distinct subsets of these patients.
  
  
  RESULTS
  Patients in whom no aneurysm is revealed on the initial angiogram can be subdivided mainly according to the pattern of hemorrhage on an early CT scan. In two thirds of these patients the CT scan shows a perimesencephalic pattern of hemorrhage (ie, blood confined to the cisterns around the midbrain); these patients invariably have a good prognosis, which obviates the need for a second angiogram. Patients with diffuse or anteriorly located blood on CT scan are at risk of rebleeding. In most of these patients the source of hemorrhage is an occult aneurysm, but intracranial artery dissections, dural arteriovenous malformations, mycotic aneurysms, trauma, bleeding disorders, substance abuse, or a cervical origin of the hemorrhage should also be considered. Patients with no blood revealed on an early CT scan but with xanthochromic cerebrospinal fluid are extremely rare. These patients deserve a second reading of the scan for blood in the prepontine cistern, which can be the only site of hemorrhage in perimesencephalic hemorrhage.
  
  
  CONCLUSIONS
  The prognosis and management of patients in whom no aneurysm is found on the initial angiogram depends on the pattern of hemorrhage on the initial CT scan. Patients should no longer be designated with the umbrella term "angiogram-negative subarachnoid hemorrhage."
authors.affiliation: University Department of Neurology, Utrecht, The Netherlands.
authors.forename: G J
authors.initials: GJ
authors.lastname: Rinkel
authors.forename: J
authors.initials: J
authors.lastname: van Gijn
authors.forename: E F
authors.initials: EF
authors.lastname: Wijdicks
mesh_terms: D000755:Anemia, Sickle Cell / Q000150:complications; D000784:Aortic Dissection / Q000150:complications / Q000000981:diagnostic imaging; D000785:Aneurysm, Infected / Q000150:complications / Q000000981:diagnostic imaging; D001165:Arteriovenous Malformations / Q000150:complications / Q000000981:diagnostic imaging; D001778:Blood Coagulation Disorders / Q000150:complications; D002340:Carotid Artery Diseases / Q000150:complications / Q000000981:diagnostic imaging; D003042:Cocaine / Q000009:adverse effects; D004388:Dura Mater / Q000098:blood supply; D006801:Humans; D002532:Intracranial Aneurysm / Q000150:complications / Q000000981:diagnostic imaging*; D013116:Spinal Cord / Q000098:blood supply; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging* / Q000209:etiology; D014057:Tomography, X-Ray Computed; D014711:Vertebral Artery / Q000000981:diagnostic imaging
chemical_list: D003042:Cocaine