title: Defining the Limits of Endoscopic Access to Internal Auditory Canal.
abstract: OBJECTIVE
  To quantify surgical access to the internal auditory canal (IAC) using an exclusively endoscopic transcanal approach (EETA) and investigate surgically relevant relationships with neurovascular and osseous landmarks of the temporal bone.
  
  
  METHODS
  Anatomical dissection of two paired temporal bones and 15 unpaired temporal bones was performed using an exclusively endoscopic approach to IAC. The dissection proceeded until the cerebellopontine angle (CPA) could be accessed. Following dissection, all the specimens were subjected to computed tomography (CT) imaging. Anatomage InVivo5 software was used to analyze the CT scans and record measurements.
  
  
  RESULTS
  CPA access and visualization of the labyrinthine segment of the facial nerve were achieved in all specimens. The mean distances from the carotid artery, jugular bulb, and middle fossa to the surgical opening (or fundostomy) of IAC were 4.1±1.5, 6.4±2.5, and 5.5±1.9 mm, respectively. The mean cross-sectional areas of the fundostomy and tympanic ring were 30.8±10.4 and 67.7±11.3 mm2. The mean distances from the osteo-cartilaginous junction and tympanic ring to the porus acusticus were 29±2.6 and 21±2.3 mm, respectively.
  
  
  CONCLUSIONS
  Transcanal access to the entire IAC can be safely achieved using an exclusively endoscopic approach. Generous removal of the cochlear promontory can be accomplished while a safe distance is maintained from key neurovascular structures. EETA to IAC offers a minimally invasive alternative to patients without serviceable hearing for intrameatal and medial IAC tumors. Increased knowledge of crucial anatomical relationships involved in this approach will facilitate acceptance and utilization.
authors.affiliation: Department of Otology and Skull Base Surgery, House Ear Clinic, California, USA. mkcosetti@yahoo.com.
authors.forename: Adam
authors.initials: A
authors.lastname: Master
authors.forename: Mickie
authors.initials: M
authors.lastname: Hamiter
authors.forename: Maura
authors.initials: M
authors.lastname: Cosetti
mesh_terms: D002102:Cadaver; D002530:Cerebellopontine Angle / Q000000981:diagnostic imaging / Q000601:surgery*; D004210:Dissection; D007758:Ear, Inner / Q000000981:diagnostic imaging / Q000601:surgery*; D004724:Endoscopy; D006801:Humans; D021621:Imaging, Three-Dimensional; D014057:Tomography, X-Ray Computed