title: Anterior inferior petrosectomy: defining the role of endonasal endoscopic techniques for petrous apex approaches.
abstract: OBJECTIVE
  Historically, surgery to the petrous apex has been addressed via craniotomy and open microscopic anterior petrosectomy (OAP). However, with the popularization of endoscopic approaches, the petrous apex can further be approached endonasally by way of an endoscopic endonasal anterior petrosectomy (EAP). Endonasal anterior petrosectomy is a relatively new procedure and has not been compared anatomically with OAP. The authors hypothesized that the EAP and OAP techniques approach different portions of the petrous apex and therefore may have different applications.
  
  
  METHODS
  Four cadaveric heads were used. An OAP was performed on one side and an EAP was performed on the contralateral side; the limits of bony resection were defined. The extent of bony resection was then evaluated using predissection and postdissection thin-slice CT scans. The comparative resection was then reconstructed using 3D modeling on Brainlab workstations.
  
  
  RESULTS
  The average resection volumes for EAP and OAP were 0.297 cm(3) and 0.649 cm(3), respectively, representing a comparative percentage of 46% (EAP/OAP). An EAP and OAP achieved resection of 29% and 64% of the total petrous apex volume, respectively. Indeed, EAP addressed the inferior portion of the petrous apex located adjacent to the petroclival suture more completely than OAP, where 45% of the bone overlying the petroclival suture (petroclival angle to the jugular foramen) was resected with the EAP, while 0% was resected with the OAP.
  
  
  CONCLUSIONS
  In anatomically normal cadavers, OAP achieved nearly a 50% larger volumetric resection than EAP. Furthermore, while OAP appears to completely address the superior portion of the petrous apex, EAP appears to have a niche in approaches to lesions in the inferior petrous apex. Given these results, the authors propose that OAP be redefined as the "superior anterior petrosectomy," while EAP be referred to as the "inferior anterior petrosectomy," which more clearly defines the role of each approach in anterior petrosectomy.
authors.affiliation: Department of Neurosurgery and Brain Repair and.
authors.forename: Jamie J
authors.initials: JJ
authors.lastname: Van Gompel
authors.forename: Puya
authors.initials: P
authors.lastname: Alikhani
authors.forename: Mark H
authors.initials: MH
authors.lastname: Tabor
authors.forename: Harry R
authors.initials: HR
authors.lastname: van Loveren
authors.forename: Sivero
authors.initials: S
authors.lastname: Agazzi
authors.forename: Sebastien
authors.initials: S
authors.lastname: Froelich
authors.forename: A Samy
authors.initials: AS
authors.lastname: Youssef
mesh_terms: D002102:Cadaver; D006801:Humans; D008866:Microsurgery / Q000379:methods; D009296:Nasal Cavity / Q000000981:diagnostic imaging; D057605:Natural Orifice Endoscopic Surgery / Q000379:methods*; D019635:Neurosurgical Procedures / Q000379:methods*; D010579:Petrous Bone / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed
keywords: EAP = endonasal anterior petrosectomy; GSPN = greater superficial petrosal nerve; IAC = internal auditory canal; ICA = internal carotid artery; OAP = open microscopic anterior petrosectomy; anterior petrosectomy; endoscopic; microsurgery; skull base