title: HRCT Correlation with Round Window Identification during Cochlear Implantation in Children.
abstract: OBJECTIVE
  To determine the accuracy of High Resolution Computer Tomography (HRCT) temporal bone measurements in predicting the actual visualization of round window niche as viewed through posterior tympanotomy (i.e. facial recess).
  
  
  METHODS
  This is a prospective study of 37 cochlear implant candidates, aged between 1and 6 years, who were referred for HRCT temporal bone during the period December 2013 to July 2014. Cochlear implantation was done in 37 children (25 in the right ear and 12 in the left ear). The distance between the short process of incus and the round window niche and the distance between the oval window and the round window niche were measured preoperatively on sub-millimeter (0.7 mm) HRCT images. We classified the visibility of round window niche based on the surgical view (i.e. through posterior tympanotomy) during surgery into three types: 1) Type 1- fully visible, 2) Type 2- partially visible, and 3) Type 3- difficult to visualize. The preoperative HRCT measurements were used to predict the type of visualization of round window niche before surgery and correlated with the findings during surgery.
  
  
  RESULTS
  The mean and standard deviation for the distance between the short process of incus and the round window niche and for the distance between the oval window and the round window niche for Types 1, 2, and 3 were 8.5 ± 0.2 mm and 3.2 ± 0.2 mm, 8.0 ± 0.4 mm and 3.8 ± 0.2 mm, 7.5 ± 0.2 mm and 4.4 ± 0.2 mm respectively, and showed statistically significant difference (P < 0.01) between them. The preoperative HRCT measurements had a sensitivity and specificity of 92.3% and 96.2%, respectively, in determining the actual visualization of round window niche.
  
  
  CONCLUSIONS
  This study shows preoperative HRCT temporal bone measurements are useful in predicting the actual visualization of round window niche as viewed through posterior tympanotomy.
authors: Department of Radiology and Imaging Sciences, Sri Ramachandra University, Chennai, Tamil Nadu, India.
authors: Sai Kiran
authors: SK
authors: Pendem
authors: Department of Radiology and Imaging Sciences, Sri Ramachandra University, Chennai, Tamil Nadu, India.
authors: Rajeswaran
authors: R
authors: Rangasami
authors: Department of ENT, Head and Neck Surgery, Sri Ramachandra University, Chennai, Tamil Nadu, India.
authors: Ravi Kumar
authors: RK
authors: Arunachalam
authors: Department of Radiology and Imaging Sciences, Sri Ramachandra University, Chennai, Tamil Nadu, India.
authors: Venkata Sai Pulivadulu
authors: VS
authors: Mohanarangam
authors: Department of Radiology and Imaging Sciences, Meenakshi Medical College, Chennai, Tamil Nadu, India.
authors: Paarthipan
authors: P
authors: Natarajan
keywords: Facial recess; round window niche; short process of incus