title: Pre-mesencephalic subarachnoid hemorrhage: rupture of tiny aneurysms of the basilar artery perforator.
abstract: OBJECTIVE
  Subarachnoid hemorrhage (SAH) around the midbrain without evidence of aneurysm, a so-called perimesencephalic SAH, has been considered a typical nonaneurysmal SAH. Recently, we have encountered several patients with SAHs that could have been classified as having perimesencephalic SAH, but a common cause of the bleeding was demonstrated. In this article, we describe clinical and radiologic characteristics of these patients.
  
  
  METHODS
  Clinical and radiologic data from patients with spontaneous SAH (total number 339) who were treated at Seoul National University Bundang Hospital between May 2003 and December 2007 were reviewed.
  
  
  RESULTS
  Of the 13 patients that could be classified as having perimesencephalic SAH, three had common radiologic features that were distinct from others. On computed tomography, the main hemorrhage (hematoma) was found localized in front of the midbrain (interpeduncular and/or peduncular cistern). Angiographically, the cause of the bleeding was not seen on conventional views and rotational angiograms. In three-dimensional reconstructed angiographic images, very small-sized (tiny) aneurysmal lesions were visible at the origin of mesencephalic perforators from the basilar artery. All the aneurysms were positioned at the exact site corresponding to the pre-mesencephalic clots. Follow-up angiography was performed on the three patients and all showed complete disappearance of the lesions at 1 month, 15 months, and 16 months follow-up, respectively.
  
  
  CONCLUSIONS
  Based on our experience, we suggest a subtype of spontaneous SAH that has unique hemorrhage localization (pre-mesencephalic cistern), specific cause (tiny aneurysms at the origin of the mesencephalic perforator), and a common benign clinical course.
authors.affiliation: Department of Neurosurgery, Korea Cancer Center Hospital, Seoul, Korea.
authors.forename: Sukh Que
authors.initials: SQ
authors.lastname: Park
authors.forename: O-Ki
authors.initials: OK
authors.lastname: Kwon
authors.forename: Seong Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Chang Wan
authors.initials: CW
authors.lastname: Oh
authors.forename: Moon Hee
authors.initials: MH
authors.lastname: Han
mesh_terms: D000368:Aged; D017542:Aneurysm, Ruptured / Q000000981:diagnostic imaging / Q000473:pathology*; D001488:Basilar Artery / Q000000981:diagnostic imaging / Q000473:pathology; D001933:Brain Stem / Q000098:blood supply* / Q000473:pathology*; D002533:Cerebral Angiography; D002941:Circle of Willis / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D008636:Mesencephalon / Q000098:blood supply / Q000000981:diagnostic imaging / Q000473:pathology; D008875:Middle Aged; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000473:pathology*; D013346:Subarachnoid Space / Q000000981:diagnostic imaging / Q000473:pathology