Distance between the middle turn of cochlea and labyrinthine portion of the facial nerve: A surgical-radiologic comparison and clinical importance.

Abstract

AbstractObjectiveTo highlight the close anatomical relationship between the middle turn of the cochlea and the labyrinthine segment of the facial nerve, which will be helpful to predict the probability of occurrence of facial nerve stimulation following cochlear implant surgery.MethodsHigh-resolution computed tomography of 40 cadaveric temporal bones was performed, followed by microscopic dissection. Cochleo-facial distance was measured with the help of a Digital Imaging and Communications in Medicine (‘DICOM’) viewer on high-resolution computed tomography and by a millimetre scale in the dissected specimen.ResultsThe cochleo-facial distance on high-resolution computed tomography was 0.62 ± 0.09 mm, ranging from 0.41 to 0.81 mm, and on dissection it was 0.57 ± 0.10 mm, ranging from 0.35 to 0.74 mm.ConclusionThe labyrinthine segment is the most likely area of stimulation in patients suffering from facial nerve stimulation following cochlear implantation. Pre-operative high-resolution computed tomography of the temporal bone can be used to examine the bone separating the labyrinthine segment of the facial nerve from the middle turn of the cochlea. This has clinical significance regarding implant side selection and pre-operative patient counselling.