title: Aberrant course of the intracranial facial nerve in cases of atresia of the internal auditory canal (IAC).
abstract: BACKGROUND
  The aim of this study is to describe the morphology of the rare malformation that is atresia of the internal auditory canal (IAC) and determine the course of the facial nerve in cases of normal facial nerve function.
  
  
  METHODS
  Index cases were retrospectively selected from our electronic database in which all inner ear malformations presenting to a tertiary referral center between 1995 and 2010 are collected. Computed tomography (CT) data and magnetic resonance (MR) images were reviewed by two neuroradiologists. An otolaryngologist analyzed the patients' clinical data.
  
  
  RESULTS
  Nine ears of six patients (three bilateral, three unilateral) with atresia of the IAC were identified. All patients presented with sensory neural hearing loss. Two of these unilaterally affected patients had facial nerve palsy. In the other seven cases of complete atresia of the IAC, the facial nerve was dislocated in its cisternal segment close to the trigeminal nerve. Where the nerve fibers enter the Gasserian ganglion, the facial nerve takes a sharp lateral turn and enters a minute canal by which it reaches the geniculate ganglion. In the two ears with facial nerve palsy, this pathway could not be identified.
  
  
  CONCLUSIONS
  In atresia of the IAC, the facial nerve takes a ventral and superior course, with its own canal starting at the point where the trigeminal nerve enters the Gasserian ganglion. Facial nerve palsy points to absence of this aberrant temporal facial nerve canal.
authors: Department of Diagnostic and Interventional Neuroradiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. Giesemann.Anja@mh-hannover.de
authors: Anja Maria
authors: AM
authors: Giesemann
authors: Jürgen
authors: J
authors: Neuburger
authors: Heinrich
authors: H
authors: Lanfermann
authors: Friedrich
authors: F
authors: Goetz
mesh_terms: D002675:Child, Preschool; D007758:Ear, Inner / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D005154:Facial Nerve / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D005158:Facial Paralysis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed