title: Prominent laterality of the posterior cerebral artery at three-dimensional time-of-flight MR angiography in M1-segment middle cerebral artery occlusion.
abstract: OBJECTIVE
  Three-dimensional time-of-flight MR angiography (3D TOF MRA) often discloses prominent posterior cerebral artery (PCA) laterality in the setting of M1-segment middle cerebral artery (MCA) occlusion. We sought to analyze the implications of prominent PCA laterality at 3D TOF MRA.
  
  
  METHODS
  We retrospectively reviewed 3D TOF MRA and digital subtraction angiography (DSA) findings in 25 patients (12 male, 13 female; mean age, 68.8 years [age range, 29-94 years]) with M1-segment occlusion. The observable laterality of the PCA, determined on the basis of 3D TOF MRA findings, was scored according to distal signal extent and compared with findings of collateral flow from the ipsilateral PCA via the leptomeningeal anastomosis (LMA) at DSA. Frequency of PCA laterality at 3D TOF MRA in patients and that in 56 healthy control subjects was also compared.
  
  
  RESULTS
  The positive predictive value of PCA laterality for the existence of collateral flow was 99.9% and the negative predictive value 30.7%. The distal extent of ipsilateral PCA signal at 3D TOF MRA positively correlated with the grade of collateral flow from the PCA via the LMA (r = 0.802; P <.01). PCA laterality was significantly less common in control subjects (P <.01).
  
  
  CONCLUSIONS
  Prominent PCA laterality at 3D TOF MRA in patients with M1-segment occlusion represents the existence of collateral flow from the PCA via the LMA.
authors.affiliation: Department of Radiology, Kameda Medical Center, Kamogawa, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Uemura
authors.forename: Toshihiro
authors.initials: T
authors.lastname: O'uchi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: Naobumi
authors.initials: N
authors.lastname: Yashiro
authors.forename: Nobumaro
authors.initials: N
authors.lastname: Ihara
authors.forename: Kazufusa
authors.initials: K
authors.lastname: Shoji
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015901:Angiography, Digital Subtraction; D003097:Collateral Circulation / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D020244:Infarction, Middle Cerebral Artery / Q000175:diagnosis* / Q000503:physiopathology*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D020769:Posterior Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013223:Statistics as Topic