title: Nontumorous Enlargement of the Internal Auditory Canal: A Risk Factor for Sensorineural Hearing Loss? A High Resolution CT-Study.
abstract: OBJECTIVE
  First aim of the study was to define normal shape and diameter of the internal auditory canal (IAC). In the second part the clinical relevance of IAC-enlargement was analyzed, considering also lesions of the subtle structures at the fundus of the internal auditory canal.
  
  
  METHODS
  440 high resolution CT-scans of the temporal bone were used for retrospective analysis of the internal auditory canal and its fundus region.
  
  
  RESULTS
  The mean value of the IAC diameter in axial and coronal plane was determined. In 20 of 440 patients IAC enlargement was found. In the group with pronounced enlargement (3fold SD) nearly all patients suffered from hearing impairment. In some of them we found structural abnormalities near the IAC fundus in the CSF/perilymph border zone.
  
  
  CONCLUSIONS
  A new CT-based definition of normal shape and diameter of the internal auditory canal is presented. There is some evidence that a pathologic transmission of CSF-pressure in case of IAC-enlargement and/or abnormal fistulous communications could play an important role in the pathophysilogy of hearing loss.
  
  
  CONCLUSIONS
  • New CT-based definition of normal internal auditory canal.• Nearly all patients showing pronounced IAC-enlargement suffer from hearing impairment.• Possible pathomechanism: Transmission of CSF-pressure on the inner ear.
authors.affiliation: Department of Radiology, Klinikum rechts der Isar Technical University Munich, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Stimmer
authors.affiliation: ENT-Clinic, Klinikum rechts der Isar, Technical University Munich, 81675 Munich, Germany.
authors.forename: H P
authors.initials: HP
authors.lastname: Niedermeyer
authors.affiliation: Institute for medical Statistics and Epidemiology, Klinikum rechts der Isar, Technical University Munich, 81675 Munich, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Kehl
authors.affiliation: Department of Radiology, Klinikum rechts der Isar, Technical University Munich, 81675 Munich, Germany.
authors.forename: E J
authors.initials: EJ
authors.lastname: Rummeny
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004424:Ear Canal / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D004428:Ear Neoplasms / Q000000981:diagnostic imaging; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis*; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013701:Temporal Bone / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D036542:Tomography, Spiral Computed; D055815:Young Adult