title: A new, more accurate classification of middle cerebral artery aneurysms: computed tomography angiographic study of 1,009 consecutive cases with 1,309 middle cerebral artery aneurysms.
abstract: BACKGROUND
  Classification of middle cerebral artery (MCA) aneurysms is sometimes difficult because the identification of the main MCA bifurcation, the key for accurate classification of MCA aneurysms, is inconsistent and somewhat subjective.
  
  
  OBJECTIVE
  To use the meeting point of the M1 and M2 trunks as an objective, generally accepted, and angiographically evident hallmark for identification of MCA bifurcation and more accurate classification of MCA aneurysms.
  
  
  METHODS
  We reviewed the computed tomographic angiography data of 1009 consecutive patients with 1309 MCA aneurysms. The M2 trunks were followed proximally until their meeting with the M1 trunk at the main MCA bifurcation. The aneurysms were classified according to their relative location: proximal, at, or distal to the MCA bifurcation. The M1 aneurysms were further subgrouped into M1 early cortical branch aneurysms and M1 lenticulostriate artery aneurysms, extending the classic 3-group classification of MCA aneurysms into a 4-group classification.
  
  
  RESULTS
  The main MCA bifurcation was the most common location for MCA aneurysms, harboring 829 aneurysms (63%). The 406 M1 aneurysms comprised 242 M1 early cortical branch aneurysms (60%) and 164 M1 lenticulostriate artery aneurysms (40%). We found 106 MCA aneurysms (8%) at the origin of large early frontal branches simulating M2 trunks liable to be misclassified as MCA bifurcation aneurysms. Even though 51% of the 407 ruptured MCA aneurysms were associated with an intracerebral hematoma, this did not affect the classification.
  
  
  CONCLUSIONS
  Studying MCA angioarchitecture and applying the 4-group classification of MCA aneurysms is practical and facilitates the accurate classification of MCA aneurysms, helping to improve surgical outcome.
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland. ahmed.elsharkawy@hus.fi
authors.forename: Ahmed
authors.initials: A
authors.lastname: Elsharkawy
authors.forename: Martin
authors.initials: M
authors.lastname: Lehečka
authors.forename: Mika
authors.initials: M
authors.lastname: Niemelä
authors.forename: Romain
authors.initials: R
authors.lastname: Billon-Grand
authors.forename: Hanna
authors.initials: H
authors.lastname: Lehto
authors.forename: Riku
authors.initials: R
authors.lastname: Kivisaari
authors.forename: Juha
authors.initials: J
authors.lastname: Hernesniemi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography / Q000706:statistics & numerical data*; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging*; D015588:Observer Variation; D015995:Prevalence; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D055815:Young Adult