Cochlear-Carotid Interval: Bridging Surgical Insights and Radiological Findings in Cadaveric Human Temporal Bones

The temporal bone is a complex neurovascular structure. The procedure of cochlear implantation is performed with in few millimetres of area around which important structures like internal carotid artery, jugular bulb and facial nerve are present. Displacement of an electrode into the carotid canal although rare is considered as a major complication in cochlear implant surgery. The purpose of this study is to highlight the close anatomic relationship (radiologically as well as on cadaveric temporal bone dissection) between the cochlea and the carotid canal and its variations which will be helpful during cochlear implant (CI) surgery to prevent injury to internal carotid artery. This study was done in SMS Medical College and Hospital, Jaipur, India. High resolution computed tomography (HRCT) of cadaveric temporal bones was done after getting permission from ethical committee of the institute. 40 bones were studied. Cochlear carotid interval (CCI) was measured with the help of dicom reader and the same temporal bones were dissected under microscope and CCI was measured with help of millimetre scale. The CCI was found to be 2.08 ± 0.89 mm and it was ranging from 0.48 to 4.25 mm on HRCT temporal bone and on dissection 2.19 ± 0.85 mm and it was ranging from 0.85 to 4.12 mm. With the increasing popularity of CI surgeries, the importance of the CCI has become more pronounced, highlighting the need for meticulous surgical planning and technique. To the best of our knowledge this is the first study of CCI which is correlating radiological and dissection anatomy of CCI.