title: Planer orientation of the bilateral semicircular canals in dizzy patients.
abstract: OBJECTIVE
  Recent development of 3-dimensional analysis of eye movement enabled to detect the eye rotation axis, which is used to determine the responsible semicircular canal(s) in dizzy patients. Therefore, the knowledge of anatomical orientation of bilateral semicircular canals is essential, as all 6 canals influence the eye movements.
  
  
  METHODS
  Employing the new head coordinate system suitable for MR imaging, we calculated the angles of semicircular canal planes of both ears in 11 dizzy patients who had normal caloric response in both ears.
  
  
  RESULTS
  The angles between adjacent canal pairs were nearly perpendicular in both ears. The angle between the posterior canal planes and head sagittal plane was 51° and significantly larger the angle between the anterior canal planes and head sagittal plane, which was 35°. The angle between the horizontal canal plane and head sagittal plane was almost orthogonal. Pairs of contralateral synergistic canal planes were not parallel, forming 10° between right and left horizontal canal planes, 17° between right anterior and left posterior canal planes and 19° between the right posterior and left anterior canal planes.
  
  
  CONCLUSIONS
  Our measurement of the angles of adjacent canal pairs and the angle between each semicircular canal and head sagittal plane coincided with those of previous reports obtained from CT images and skull specimens. However, the angles between contralateral synergistic canal planes were more parallel than those of previous reports.
authors.affiliation: Department of Otolaryngology, Tokyo Women's Medical University, Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo, Japan. sachikoaoki@jewel.ocn.ne.jp
authors.forename: Sachiko
authors.initials: S
authors.lastname: Aoki
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Takei
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Suzuki
authors.forename: Ai
authors.initials: A
authors.lastname: Masukawa
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Arai
mesh_terms: D000328:Adult; D000368:Aged; D002150:Caloric Tests; D004244:Dizziness / Q000473:pathology*; D053483:Eye Movement Measurements; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012665:Semicircular Canals / Q000033:anatomy & histology* / Q000473:pathology*