title: Segments of the internal carotid artery during endoscopic transnasal and open cranial approaches: can a uniform nomenclature apply to both?
abstract: BACKGROUND
  The classic anatomic view of the course of the internal carotid artery (ICA) and its segments familiar to neurosurgeons by a 3-dimensional microscopic cranial view may be challenging to understand when seen in the unique 2-dimensional view of transnasal endoscopic surgery.
  
  
  OBJECTIVE
  We re-examined our 1996 classification of 7 (C1-C7) segments of the ICA, comparing the arterial course in cadaveric dissections for both a transnasal endoscopic transpenoidal approach and frontotemporal craniotomy.
  
  
  METHODS
  Five formalin-fixed cadaveric heads injected with colored silicone underwent thin-cut computed tomographic scanning for bony and vascular analysis. The ICA's intracranial course viewed by transnasal endoscopic dissection was compared with the view of a bilateral frontotemporal crantiotomy, from the petrous (C2) to communicating (C7) segments.
  
  
  RESULTS
  Refinement of our 1996 ICA classification provides an anatomical understanding for endoscopic exposures transnasally along an inferior skull base trajectory. The changing course of the ICA, initially termed loop is now termed bend (i.e., implying a change in direction). Four bends are described as the ICA enters into the skull base as C2, C3-C4, C4, and C4-C5. We discuss delineation of certain problematic ICA segments and identify landmarks for endoscopic endonasal approaches.
  
  
  CONCLUSIONS
  Our classification of the segments of the ICA achieves consistency without sacrificing either clinical or anatomic accuracy for either transcranial or endoscopic approaches. Universal application of this established nomenclature can avoid new and misleading terms, respects anatomical landmarks delineating segments, and provides a universal language for clear communication between disciplines.
authors.affiliation: Department of Neurosurgery, University of Cincinnati (UC) Neuroscience Institute and UC College of Medicine, Cincinnati, Ohio, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: DePowell
authors.affiliation: Department of Neurosurgery, Lariboisiere University Hospital, Paris, France.
authors.forename: Sebastien C
authors.initials: SC
authors.lastname: Froelich
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Brain Tumor Center at the University of Cincinnati (UC) Neuroscience Institute and UC College of Medicine, Cincinnati, Ohio, USA.
authors.forename: Lee A
authors.initials: LA
authors.lastname: Zimmer
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 Otolaryngology - Head and Neck Surgery, University of Grenoble, Grenoble, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Karkas
authors.affiliation: Department of Neurosurgery, University of Cincinnati (UC) Neuroscience Institute and UC College of Medicine, 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 (UC) Neuroscience Institute and UC College of Medicine, Cincinnati, Ohio, USA; Mayfield Clinic, Cincinnati, Ohio, USA. Electronic address: editor@mayfieldclinic.com.
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Keller
mesh_terms: D002102:Cadaver; D002343:Carotid Artery, Internal / Q000601:surgery*; D003399:Craniotomy / Q000379:methods*; D004724:Endoscopy / Q000379:methods*; D009296:Nasal Cavity / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000379:methods*; D009626:Terminology as Topic
keywords: Endoscopic transnasal approach; Internal carotid artery; Nomenclature