title: Two indices affecting the directions of the sylvian fissure dissection in middle cerebral artery bifurcation aneurysms.
abstract: OBJECTIVE
  This study proposes more objective methods for deciding the appropriate direction of the sylvian fissure dissection during surgical clipping in middle cerebral artery (MCA) bifurcation aneurysms.
  
  
  METHODS
  We reviewed data of 36 consecutive patients with MCA bifurcation aneurysms. We measured 2 indices preoperatively on 3-dimensional computed tomography angiography (3D-CTA). Analysis of the calculated data allowed us to select the appropriate direction of sylvian fissure dissection for ease of proximal control of M1. Statistically, Mann-Whitney test was used.
  
  
  RESULTS
  We classified subjects into 2 groups based on the technical level of M1 exposure during surgical clipping. When it was difficult to expose M1, subjects were assigned to Group I, and Group II were subjects in whom M1 exposure was easy. The mean difference between the distances extending from the limbus sphenoidale (LS) line to the internal carotid artery bifurcation and extending from the LS line to the MCA bifurcation was 1.00 ± 0.42 mm in group I and 4.39 ± 2.14 mm in group II. The mean M1 angle was 9.36 ± 3.73° in the group I and 34.05 ± 16.71° in the group II (M1 slope gap p < 0.05, M1 angle p < 0.05).
  
  
  CONCLUSIONS
  We have found an objective method for preoperatively verifying ease of exposure of M1 artery during surgical clipping. Therefore, we suggest use of the preoperative M1 slope gap and M1 angle as indicators in 3D-CTA selecting the direction of sylvian fissure dissection for easy proximal control of M1.
authors.affiliation: Department of Neurosurgery, Eulji University Hospital, College of Medicine, Eulji University, Taejon, Korea.
authors.forename: Hyun Wook
authors.initials: HW
authors.lastname: Park
authors.forename: Seung Young
authors.initials: SY
authors.lastname: Chung
authors.forename: Moon Sun
authors.initials: MS
authors.lastname: Park
authors.forename: Seong Min
authors.initials: SM
authors.lastname: Kim
authors.forename: Byul Hee
authors.initials: BH
authors.lastname: Yoon
authors.forename: Han Kyu
authors.initials: HK
authors.lastname: Kim
keywords: Dissecting; Intracranial aneurysm; Middle cerebral artery; Three-dimensional cerebral angiography