title: Meningeal layers around anterior clinoid process as a delicate area in extradural anterior clinoidectomy : anatomical and clinical study.
abstract: OBJECTIVE
  Removal of the anterior clinoid process (ACP) is an essential process in the surgery of giant or complex aneurysms located near the proximal internal carotid artery or the distal basilar artery. An extradural clinoidectomy must be performed within the limits of the meningeal layers surrounding the ACP to prevent morbid complications. To identify the safest method of extradural exposure of the ACP, anatomical studies were done on cadaver heads.
  
  
  METHODS
  Anatomical dissections for extradural exposure of the ACP were performed on both sides of seven cadavers. Before dividing the frontotemporal dural fold (FTDF), we measured its length from the superomedial apex attached to the periorbita to the posterolateral apex which connects to the anterosuperior end of the cavernous sinus.
  
  
  RESULTS
  The average length of the FTDF on cadaver dissections was 7 mm on the right side and 7.14 mm on the left side. Cranial nerves were usually exposed when cutting FTDF more than 7 mm of the FTDF.
  
  
  CONCLUSIONS
  The most delicate area in an extradural anterior clinoidectomy is the junction of the FTDF and the anterior triangular apex of the cavernous sinus. The FTDF must be cut from the anterior side of the triangle at the periorbital side rather than from the dural side. The length of the FTDF incision must not exceed 7 mm to avoid cranial nerve injury.
authors.affiliation: Department of Neurosurgery, Eulji University Hospital, Daejeon, Korea.
authors.forename: Byul Hee
authors.initials: BH
authors.lastname: Yoon
authors.forename: Han Kyu
authors.initials: HK
authors.lastname: Kim
authors.forename: Mun Sun
authors.initials: MS
authors.lastname: Park
authors.forename: Seong Min
authors.initials: SM
authors.lastname: Kim
authors.forename: Seung Young
authors.initials: SY
authors.lastname: Chung
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lanzino
keywords: Anatomical study; Extradural clinoidectomy; Frontotemporal dural fold; Superior orbital fissure