title: Identification of Onodi cell and new classification of sphenoid sinus for endoscopic sinus surgery.
abstract: BACKGROUND
  There is no effective classification method for the opening of the sphenoid sinus. The objective of this study was to examine the effectiveness of identification of the Onodi cell and classification of the sphenoid sinus using sagittal computed tomography (CT) for sphenoidotomy.
  
  
  METHODS
  CT images of the sinuses of surgical patients (n = 261; 522 sides) were studied. Using sagittal CT, the relationships between the lateral side of the anterior wall of the sphenoid sinus and the optic nerve, and between the middle of the anterior wall of the sphenoid sinus and the skull base or pituitary gland were studied. Images were classified as demonstrating skull base (without the Onodi cell), optic canal, sella, or infra-sella (all with the Onodi cell) type.
  
  
  RESULTS
  Two hundred and fifty-eight sides (49.2%) were of the skull-base type, 181 (34.7%) were of the optic-canal type, 58 (11.1%) were of the sella type, and 26 (5.0%) were of the infra-sella type; ie, the Onodi cell was present in 50.8% of sides. The width of the anterior wall of the sphenoid sinus became narrower as it shifted from the skull-base type to the infra-sella type.
  
  
  CONCLUSIONS
  Classification of the anterior wall of the sphenoid sinus based on the Onodi cell allows 3-dimensional assessment of the shape of the sphenoid sinus. We believe that the sphenoid sinus can be opened safely by full preoperative assessment of the anterior wall type, the position of the superior turbinate, and the position of the ostium of the sphenoid sinus.
authors.affiliation: Department of Otorhinolaryngology, Toho University, Tokyo, Japan.
authors.forename: Kota
authors.initials: K
authors.lastname: Wada
authors.affiliation: Department of Otorhinolaryngology, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Moriyama
authors.affiliation: Department of Otorhinolaryngology, Toho University, Tokyo, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Edamatsu
authors.affiliation: Department of Otorhinolaryngology, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Hama
authors.affiliation: Department of Otorhinolaryngology, Toho University, Tokyo, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Arai
authors.affiliation: Department of Otorhinolaryngology, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Kojima
authors.affiliation: Department of Otorhinolaryngology, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Otori
authors.affiliation: Department of Otorhinolaryngology, St. Luke's International Hospital, Tokyo, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Yanagi
mesh_terms: D004724:Endoscopy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D013100:Sphenoid Bone / Q000000981:diagnostic imaging / Q000473:pathology*; D013101:Sphenoid Sinus / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D014057:Tomography, X-Ray Computed
keywords: Onodi cell; infra-sella type; optic nerve; optic-canal type; sella type; skull-base type; sphenoid sinus; sphenoid sinus ostium; superior turbinate