title: Extended middle fossa approach: quantitative analysis of petroclival exposure and surgical freedom as a function of successive temporal bone removal by using frameless stereotaxy.
abstract: OBJECTIVE
  Conventional wisdom regarding skull base surgery says that more extensive bone removal equals greater exposure. Few researchers have quantitatively examined this assertion, however. In this study the authors used a frameless stereotactic system to measure quantitatively the area of petroclival exposure and surgical freedom for manipulation of instruments with successive steps of temporal bone removal.
  
  
  METHODS
  With the aid of high-power magnification and a high-speed drill, 12 cadaveric specimens were dissected in four predetermined, successive bone removal steps: 1) removal of the Kawase triangle; 2) removal of the Glasscock triangle; 3) removal of the cochlea together with skeletonization of the anterior internal auditory canal; and 4) inferior displacement of the zygoma. Step 1 offered 62 +/- 43 mm2 of exposed petroclival area, with 84 +/- 69 mm2 of surgical freedom; Step 2, 61 +/- 22 and 76 +/- 58 mm2; Step 3, 128 +/- 47 and 109 +/- 87 mm2; and Step 4, 135 +/- 38 and 102 +/- 69 mm2, respectively.
  
  
  CONCLUSIONS
  The middle fossa approach provided a means surgically to expose the petroclival area. When examined quantitatively by using a frameless stereotactic device, the authors determined that the removal of the cochlea and skeletonization of the anterior internal auditory canal (Step 3) provided the most significant increase in both exposure and surgical freedom. Removal of the zygoma improved neither exposure nor surgical freedom.
authors.affiliation: Division of Skull Base Neurosurgery, Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon 97239, USA.
authors.forename: Frank P K
authors.initials: FP
authors.lastname: Hsu
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Anderson
authors.forename: Aclan
authors.initials: A
authors.lastname: Dogan
authors.forename: Joseph
authors.initials: J
authors.lastname: Finizio
authors.forename: Akio
authors.initials: A
authors.lastname: Noguchi
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Liu
authors.forename: Sean O
authors.initials: SO
authors.lastname: McMenomey
authors.forename: Johnny B
authors.initials: JB
authors.lastname: Delashaw
mesh_terms: D002102:Cadaver; D003051:Cochlea / Q000601:surgery; D004424:Ear Canal / Q000601:surgery; D006801:Humans; D019635:Neurosurgical Procedures / Q000379:methods*; D019291:Skull Base / Q000601:surgery*; D013238:Stereotaxic Techniques; D015050:Zygoma / Q000601:surgery