title: Neuro-otologic findings in unilateral isolated narrow internal auditory meatus.
abstract: OBJECTIVE
  To report neuro-otologic findings concerning the four nerves in the internal auditory meatus (IAM) in patients with isolated congenitally narrow IAM and explore the implications regarding ontogeny of the nerves in the IAM.
  
  
  METHODS
  Retrospective case series study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Five consecutive patients between 1997 and 2002 with unilateral isolated narrow IAM demonstrated by high-resolution computed tomography whose chief complaint was hearing loss (1 male and 4 females, 4 right sides and 1 left; age range 5-37 years, mean 20 years; IAM diameter at the porus: 26-33% of that on the normal side).
  
  
  METHODS
  Functional studies concerning the VIIth cranial nerve and the three branches of the VIIIth cranial nerve.
  
  
  RESULTS
  In all ears, auditory brain stem responses were absent, the speech discrimination score was 0%, and otoacoustic emissions were absent or markedly reduced compared with those on the normal side. Caloric responses were absent in two ears, reduced in two ears, and normal in one ear. Galvanic body sway tests showed no responses in the two ears in which caloric responses were absent. Inferior vestibular nerve function was estimated as normal in all ears on the basis of vestibular evoked myogenic potential recordings. Facial nerve functions were normal in all patients.
  
  
  CONCLUSIONS
  In isolated congenital stenosis of IAM, dysfunction of each nerve in the IAM can occur independently. In the ontogeny of the VIIIth cranial nerve, the cochlear and superior vestibular nerves tended to be involved together, whereas the cochlear and inferior vestibular nerves appeared independent of each other.
authors: Department of Otolaryngology, Faculty of Medicine, University of Tokyo, Tokyo, Japan. itoken-tky@umin.ac.jp
authors: Ken
authors: K
authors: Ito
authors: Sayaka
authors: S
authors: Suzuki
authors: Toshihisa
authors: T
authors: Murofushi
authors: Shin-ichi
authors: S
authors: Ishimoto
authors: Shinichi
authors: S
authors: Iwasaki
authors: Shotaro
authors: S
authors: Karino
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004424:Ear Canal / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D004594:Electrophysiology; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D034381:Hearing Loss / Q000209:etiology* / Q000503:physiopathology; D006319:Hearing Loss, Sensorineural / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous; D010469:Perceptual Distortion; D012189:Retrospective Studies; D013067:Speech Perception; D014057:Tomography, X-Ray Computed / Q000379:methods; D014722:Vestibule, Labyrinth / Q000503:physiopathology