title: Endoscopic, endonasal variability in the anatomy of the internal carotid artery.
abstract: BACKGROUND
  Classic three-dimensional schemas of the internal carotid artery (ICA) for transcranial approaches do not necessarily apply to two-dimensional endoscopic views. Modifying an existing ICA segment classification, we define endoscopic orientation for the lacerum (C3) to clinoid (C5) segments through an endonasal approach.
  
  
  METHODS
  In 20 cadaveric heads, we classified endoscopic appearance based on shape and angulation of C3 to C5 segments. Distances were measured between both arteries, and between the ICA and pituitary gland.
  
  
  RESULTS
  We identified 4 common ICA patterns: types I through III matched side-to-side, whereas type IV was asymmetric. In 80% of specimens, the pituitary gland had direct contact with the ICA. In 20% of specimens, a space existed between the pituitary gland and the cavernous segment. Access to the posterior aspect of the cavernous sinus medial to the cavernous segment was possible without retraction of the artery or pituitary gland. Spaces between the lacerum and cavernous segments were trapezoid (80%) and hourglass (20%).
  
  
  CONCLUSIONS
  Distinguishing which ICA type courses between the lacerum and clinoid segments can help clarify the relationships between the artery and its surrounding structures during endoscopic approaches. Adapting the classic terminology of ICA segments provided consistency of endoscopic relevance, defined potential endoscopic corridors, and highlighted the critical step of arterial contact.
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA; Department of Neurosurgery, Hautepierre University Hospital, Strasbourg, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Cebula
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA; Brain Tumor Center, University of Cincinnati Neuroscience Institute, Cincinnati, Ohio, USA.
authors.forename: Almaz
authors.initials: A
authors.lastname: Kurbanov
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA; Department of Otolaryngology-Head and Neck Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA; Brain Tumor Center, University of Cincinnati Neuroscience Institute, Cincinnati, Ohio, USA.
authors.forename: Lee A
authors.initials: LA
authors.lastname: Zimmer
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA; Brain Tumor Center, University of Cincinnati Neuroscience Institute, Cincinnati, Ohio, USA.
authors.forename: Pavel
authors.initials: P
authors.lastname: Poczos
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.
authors.forename: James L
authors.initials: JL
authors.lastname: Leach
authors.affiliation: Department of Neurosurgery, Pelegrina Hospital and Ossys Institut, Sección (Mendoza), Argentina.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: De Battista
authors.affiliation: Department of Neurosurgery, Lariboisiere University Hospital, Paris, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Froelich
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA; Brain Tumor Center, University of Cincinnati Neuroscience Institute, Cincinnati, Ohio, USA; Mayfield Clinic, Cincinnati, Ohio, USA.
authors.forename: Philip V
authors.initials: PV
authors.lastname: Theodosopoulos
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA; Brain Tumor Center, University of Cincinnati Neuroscience Institute, Cincinnati, Ohio, USA; Mayfield Clinic, Cincinnati, Ohio, USA. Electronic address: mary.kemper@uc.edu.
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Keller
mesh_terms: D002102:Cadaver; D002343:Carotid Artery, Internal / Q000033:anatomy & histology* / Q000601:surgery*; D002344:Carotid Body / Q000033:anatomy & histology; D004724:Endoscopy / Q000379:methods; D006801:Humans; D009296:Nasal Cavity / Q000033:anatomy & histology*; D019635:Neurosurgical Procedures / Q000379:methods; D010902:Pituitary Gland / Q000033:anatomy & histology; D009626:Terminology as Topic
keywords: Anatomic study; Classification; Endoscopic endonasal approaches; ICA segments; Pituitary gland