title: Pathologically confirmed cryptic vascular malformation as a cause of convexity subarachnoid hemorrhage:  case report.
abstract: BACKGROUND
  We report a rare case of pathologically confirmed cryptic vascular malformation as a cause of primary convexity subarachnoid hemorrhage (SAH) of unknown etiology.
  
  
  METHODS
  A 48-year-old woman presented with sudden severe headache. Localized right convexity SAH was observed on computed tomography (CT) scan, but the origin could not be detected despite extensive workup covering the entire head by using 3.0-Tesla magnetic resonance (MR) imaging with MR angiography and CT angiography combined with venous-phase imaging with a 320-detector row CT scanner. Subsequent digital subtraction angiography (DSA) performed 2.5 hours after admission failed to reveal any cause of SAH; however, a right frontoparietal avascular region was suspected to be due to a newly developed intracerebral hematoma. The lesion was simultaneously confirmed by angiographic cone-beam CT imaging. Because she remained neurologically intact, we decided to perform a follow-up study later with medical management. However, she developed left hemiparesis 3 hours after DSA. CT scan demonstrated progression of the hematoma, and her symptoms gradually worsened. Emergent surgical exploration along the SAH superficial to the postcentral sulcus and hematoma evacuation were performed, with favorable functional outcome. Pathological examination confirmed cryptic vascular malformation with several abnormally dilated arterioles within the subarachnoid space surrounded by a thick SAH clot.
  
  
  CONCLUSIONS
  It is important to consider the possibility of ruptured cryptic vascular malformation as a cause of nontraumatic nonaneurysmal convexity SAH when recurrent hemorrhage occurs despite thorough diagnostic workup, because surgical resection may be the only curative treatment option to eliminate the risk of rebleeding and disabling symptoms.
authors.affiliation: Department of Surgical Neurology, Research Institute for Brain and Blood Vessels-AKITA, Akita, Japan. tmutoh@tiara.ocn.ne.jp
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Mutoh
authors.forename: Shinya
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Junta
authors.initials: J
authors.lastname: Moroi
authors.forename: Hajime
authors.initials: H
authors.lastname: Miyata
authors.forename: Akifumi
authors.initials: A
authors.lastname: Suzuki
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yasui
mesh_terms: D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000150:complications* / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D011859:Radiography; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery*; D016896:Treatment Outcome