title: Nonaneurysmal Subarachnoid Hemorrhage Due to Unfused or Twiglike Middle Cerebral Artery Rupture: Two Case Reports.
abstract: BACKGROUND
  An unfused or twiglike middle cerebral artery (MCA) is a congenital anomaly related to the abnormal development of the MCA. An unfused or twiglike MCA can cause both ischemic and hemorrhagic strokes. Previous reports have shown that an unfused or twiglike MCA with coexisting aneurysms can cause subarachnoid hemorrhage (SAH).
  
  
  METHODS
  Two patients presented with nonaneurysmal SAH due to an unfused or twiglike MCA. Both patients had stenosis of the proximal M1 segment of the left MCA and abnormal vascular nets distal to the stenotic lesion. Vasculature distal to the abnormal vascular nets remained grossly normal. These findings were not evident in computed tomography or magnetic resonance angiography.
  
  
  CONCLUSIONS
  An unfused or twiglike MCA can cause nonaneurysmal SAH. Digital subtraction angiography is necessary for accurate diagnosis.
authors.affiliation: Department of Neurosurgery, Sendai Medical Center, Sendai, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Tashiro
authors.affiliation: Department of Neurosurgery, Sendai Medical Center, Sendai, Japan. Electronic address: tainoue@snh.go.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Department of Neurosurgery, Sendai Medical Center, Sendai, Japan.
authors.forename: Ichiyo
authors.initials: I
authors.lastname: Shibahara
authors.affiliation: Department of Neurosurgery, Sendai Medical Center, Sendai, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ezura
authors.affiliation: Department of Neurosurgery, Sendai Medical Center, Sendai, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uenohara
authors.affiliation: Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Fujimura
authors.affiliation: Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Teiji
authors.initials: T
authors.lastname: Tominaga
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015901:Angiography, Digital Subtraction; D020785:Central Nervous System Vascular Malformations / Q000150:complications* / Q000000981:diagnostic imaging; D002533:Cerebral Angiography / Q000379:methods; D000072226:Computed Tomography Angiography; D003251:Constriction, Pathologic; D005260:Female; D006801:Humans; D020765:Intracranial Arterial Diseases / Q000000981:diagnostic imaging / Q000209:etiology* / Q000628:therapy; D018810:Magnetic Resonance Angiography; D020768:Middle Cerebral Artery / Q000002:abnormalities* / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000209:etiology* / Q000628:therapy
keywords: Middle cerebral artery; nonaneurysmal; subarachnoid hemorrhage; twiglike; unfused