title: A new method of locating the optic canal based on structures in sella region: computed tomography study.
abstract: BACKGROUND
  The location of optic canal and the intracranial segment of optic nerve is difficult because of the high possibility of the deficiency of optic protuberance as well as its complex relationship to sphenoid and ethmoidal sinus. A new method of locating the optic canal and a comprehensive analysis of it and the structures around is of great importance.
  
  
  OBJECTIVE
  Our study aimed to provide a new method to locate the optic canal and analyze the relationship between optic canal and other structures in the sella region, which can be a guidance for endoscopic sinus surgery such as the optic nerve decompression and transsphenoidal approach to the pituitary adenoma and reduced complications caused by the injury of optic nerve.
  
  
  METHODS
  Computed tomography images of 120 sphenoid sinuses in adults were reviewed, and multiplanar reconstruction was used to make it possible to make the measurement in coronal, sagittal, and axial plane at the same time. The positional relationship between optic canal and the stationary structures in sella region was analyzed.
  
  
  RESULTS
  The horizontal distance between the lowest point of sella bottom (SB) and sulcus prechiasmaticus in the sagittal plane was 8.08 (SD, 0.79) mm. The distance between the medial wall of optic canal and the midline of SB were 7.01 (SD, 1.43) mm in plane 1, 7.78 (SD, 0.86) mm in plane 2, 11.08 (SD, 0.82) mm in plane 3, and 13.81 (SD, 0.66) mm in plane 4; the angles between line BO and line BC were 87.99 (SD, 5.04) degrees in plane 1, 87.71 (SD, 4.98) degrees in plane 2, 82.54 (SD, 5.78) degrees in plane 3, and 82.57 (SD, 6.99) degrees in plane 4. As for the relationship between optic canal and the sphenoid sinus, there were 2.08% of sphenoid sinus of type A, 19.17% of type B, 45.00% of type C, 17.50% of type D, and 16.25% of type E.
  
  
  CONCLUSIONS
  Optic canal can be located by the structures or markers in sella region such as the midline of SB, the lowest point of SB, the midpoint in the top edge of sphenoid sinus, and tubercular recess. The analysis of the relationship between optic canal and the sphenoid sinus as well as the data measured in our study is helpful to make an accurate location of the optic canal when the bony landmarks of optic canal are not available.
authors.affiliation: Department of Obstetrics and Gynecology, First Hospital of Jilin University, Jilin, China.
authors.forename: Haijun
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiangliang
authors.initials: X
authors.lastname: Liu
authors.forename: Ye
authors.initials: Y
authors.lastname: Cheng
authors.forename: Siwen
authors.initials: S
authors.lastname: Zhang
authors.forename: Chenyu
authors.initials: C
authors.lastname: Wang
authors.forename: Dong
authors.initials: D
authors.lastname: Cui
authors.forename: Youqiong
authors.initials: Y
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Fu
authors.forename: Yufa
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000000981:diagnostic imaging*; D012658:Sella Turcica / Q000000981:diagnostic imaging*; D013101:Sphenoid Sinus / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D055815:Young Adult