title: Analysis of pneumatization and neurovascular structures of the sphenoid sinus using cone-beam tomography (CBT).
abstract: BACKGROUND
  The sphenoid sinus is a frequent target of paranasal sinus surgery. Because of the high risk of injuring the surrounding structures (e.g. internal carotid artery, optical nerve) a preoperative imaging is absolutely necessary.
  
  
  OBJECTIVE
  To analyze the possibilities of cone-beam computed tomography (CBCT), which is especially quite a new technique in ENT, in the evaluation of the sphenoid sinus, its surrounding structures, and the corresponding anatomical variations.
  
  
  METHODS
  This was a retrospective, single-centre study of 580 patients (1160 sides = cases). The Accu-I-Tomo-F17 was used. Pneumatization of sphenoid sinus, course of internal artery, course of optical nerve, and dehiscence of the bony canals were evaluated.
  
  
  RESULTS
  In the case of pneumatization a type I (completely missing or minimal sphenoid sinus) was found in two patients (0.3%), type II (posterior wall of sphenoid sinus is in front of the anterior wall of the sella) in 38 patients (6.6%), type III (posterior wall is between anterior and posterior wall of sella) in 332 patients (57,2%), type IVa (posterior wall is behind the posterior wall of sella without air dorsal the sella) in 104 patients (17.9%), and type IVb (similar to type IVa but with air dorsal the sella) in 104 patients (17.9%). In 1025 cases (89.5%) a smooth course of the internal carotid artery was found whereas a free course could be detected in 120 cases (10.5%). Defects of the bony canal of the optical nerve were found in 16.7% and of the internal carotid artery in 2.7% of the cases. The optical nerve showed a free course through the sphenoid in 151 cases (13.7%) and a smooth course in 1007 cases (87.0%).
  
  
  CONCLUSIONS
  CBCT could evaluate all relevant anatomic structures and answer the questions of different anatomical variants. A modified classification of the pneumatization of the sphenoid sinus could be described. Frequencies of anatomical variations are in accordance with the current literature of CT research.
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, UKGM, Marburg, Germany. gueldner@staff.uni-marburg.de
authors.forename: Christian
authors.initials: C
authors.lastname: Güldner
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Pistorius
authors.forename: Isabell
authors.initials: I
authors.lastname: Diogo
authors.forename: Siegfried
authors.initials: S
authors.lastname: Bien
authors.forename: Andreas
authors.initials: A
authors.lastname: Sesterhenn
authors.forename: Jochen A
authors.initials: JA
authors.lastname: Werner
mesh_terms: D000328:Adult; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006801:Humans; D012189:Retrospective Studies; D012658:Sella Turcica / Q000000981:diagnostic imaging; D013100:Sphenoid Bone / Q000000981:diagnostic imaging; D013101:Sphenoid Sinus / Q000002:abnormalities / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000294:innervation