title: Entry point to the Sylvian fissure for the pterional transsylvian approach.
abstract: BACKGROUND
  Although the anatomy of the Sylvian fissure is understood, there is little information on where to start its dissection in the pterional transsylvian (PT-TS) approach. At small craniotomy using the PT-TS approach, we set the entry point to the Sylvian fissure at 15 mm behind the anterior edge of the craniotomy along the Sylvian fissure and designated this site "point 15." Here we compared the utility of "point 15" with the Sylvian point (point on the Sylvian fissure giving rise to the horizontal and anterior ascending rami) that had been recommended earlier as the entry site for opening the Sylvian fissure.
  
  
  METHODS
  This study includes 16 patients with 7 ruptured and 9 unruptured anterior circulation aneurysms. We evaluated the usefulness of "point 15" in the PT-TS approach for aneurysmal neck clipping with respect to the adequacy of anatomical exposure and low invasiveness.
  
  
  RESULTS
  In 12 patients "point 15" provided for excellent anatomical exposure of the Sylvian fissure; complete neck clipping was possible with minimal brain retraction and damage. In two patients with ruptured aneurysms and thick subarachnoid hemorrhage and in two patients with unruptured aneurysms, the dissection had to be enlarged 3 to 4 mm distally without reaching the Sylvian point. In the latter two patients the Sylvian veins were tethered to frontal and temporal lobes.
  
  
  CONCLUSIONS
  The "point 15" was an easily set entry point to the Sylvian fissure. It provided for sufficient anatomical exposure at surgery for anterior circulation aneurysms; additional posterior dissection was required in rare cases. We found that "point 15" was useful in small craniotomies using the PT-TS approach.
authors.affiliation: Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan. yamahata-nsu@umin.net
authors.forename: H
authors.initials: H
authors.lastname: Yamahata
authors.forename: H
authors.initials: H
authors.lastname: Tokimura
authors.forename: K
authors.initials: K
authors.lastname: Hirahara
authors.forename: T
authors.initials: T
authors.lastname: Ishii
authors.forename: T
authors.initials: T
authors.lastname: Hanada
authors.forename: H
authors.initials: H
authors.lastname: Hirano
authors.forename: R
authors.initials: R
authors.lastname: Hanaya
authors.forename: S
authors.initials: S
authors.lastname: Sugata
authors.forename: K
authors.initials: K
authors.lastname: Mamitsuka
authors.forename: K
authors.initials: K
authors.lastname: Arita
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D017542:Aneurysm, Ruptured / Q000601:surgery; D002343:Carotid Artery, Internal / Q000601:surgery; D003399:Craniotomy / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D020244:Infarction, Middle Cerebral Artery / Q000601:surgery; D002532:Intracranial Aneurysm / Q000601:surgery; D020300:Intracranial Hemorrhages / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D011446:Prospective Studies; D012886:Skull / Q000033:anatomy & histology* / Q000601:surgery*; D013100:Sphenoid Bone / Q000033:anatomy & histology; D014057:Tomography, X-Ray Computed; D055815:Young Adult