Evaluation of computed tomography parameters in patients with facial nerve stimulation post-cochlear implantation

Abstract

Purpose: To compare the preoperative computed tomography (CT) parameters, including the thickness and density of the bone separating the upper basal turn of the cochlea (UBTC) and the labyrinthine segment of the facial nerve (LSFN), in patients with and without facial nerve stimulation (FNS) in post-cochlear implants (CI). Methods: A retrospective case review of 1700 CI recipients in a tertiary referral center between January 2010 and January 2020 was performed; out of the 35 recipients who were found to have FNS, 29 were included in the study. The control group comprised the same number of randomly selected patients. CT parameters of the patients were measured independently by three fellowship-trained neuro-otologists blinded to the postoperative status of the patients. Thickness in axial and coronal views and density of the bone separating the UBTC and the LSFN were measured. Result: There was satisfactory agreement between the readings of the three reviewers. The distances (in mm) between the UBTC and LSFN obtained from the coronal (0.43 ± 0.24 vs. 0.63 ± 0.2) and axial (0.42 ± 0.25 vs. 0.6 ± 0.18) views were statistically lower in the FNS group (p = 0.001 and 0.005, respectively). The density (in HU) of the bony partition was also statistically lower in the FNS group (1038 ± 821 vs. 1409 ± 519; p = 0.029). Conclusion: Patients who experienced FNS postoperatively had significantly lower distance and bone density between the UBTC and the LSFN. This finding can help surgeons in preoperative planning in an attempt to decrease the occurrence of FNS.