title: Predictors of round window accessibility for adult cochlear implantation based on pre-operative CT scan: a prospective observational study.
abstract: BACKGROUND
  Cochlear implantation has become a mainstream treatment option for patients with severe to profound sensorineural hearing loss. During cochlear implant, there are key surgical steps which are influenced by anatomical variations between each patient. The aim of this study is to determine if there are potential predictors of difficulties that may be encountered during the cortical mastoidectomy, facial recess approach and round window access in cochlear implant surgery based upon pre-operative temporal bone CT scan.
  
  
  METHODS
  Fifty seven patients undergoing unilateral cochlear implantation were analyzed. Difficulty with 1) cortical mastoidectomy, 2) facial recess approach, and 3) round window access were scored intra-operatively by the surgeon in a blinded fashion (1 = "easy", 2 = "moderate", 3 = "difficult"). Pre-operative temporal bone CT scans were analyzed for 1) degree of mastoid aeration; 2) location of the sigmoid sinus; 3) height of the tegmen; 4) the presence of air cells in the facial recess, and 5) degree of round window bony overhang.
  
  
  RESULTS
  Poor mastoid aeration and lower tegmen position, but not the location of sigmoid sinus, are associated with greater difficulty with the cortical mastoidectomy. Presence of an air cell around the facial nerve was predictive of easier facial recess access. However, the degree of round window bony overhang was not predictive of difficulty associated with round window access.
  
  
  CONCLUSIONS
  Certain parameters on the pre-operative temporal bone CT scan may be useful in predicting potential difficulties encountered during the key steps involved in cochlear implant surgery.
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada. edward.park@utoronto.ca.
authors.forename: Edward
authors.initials: E
authors.lastname: Park
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Hosam
authors.initials: H
authors.lastname: Amoodi
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Jafri
authors.initials: J
authors.lastname: Kuthubutheen
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Chen
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Julian M
authors.initials: JM
authors.lastname: Nedzelski
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Vincent Y W
authors.initials: VY
authors.lastname: Lin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019929:Cochlear Implantation / Q000379:methods*; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D011446:Prospective Studies; D012405:Round Window, Ear / Q000000981:diagnostic imaging* / Q000601:surgery*; D013701:Temporal Bone / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D055815:Young Adult