Can Preoperative CT Scans Be Used to Predict Facial Nerve Stimulation Following CI?

OBJECTIVES: 1) To determine the ability of preoperative computed tomography (CT) to predict facial nerve stimulation (FNS) after cochlear implantation (CI). 2) To recognize the limitations of CT in predicting FNS.

STUDY DESIGN: Patient control study.

SETTING: Tertiary care academic medical center.

SUBJECTS: Adult patients with CI from 2003 to 2015.

METHODS: Patients with severe FNS (n = 4) were compared with randomly selected CI patients (n = 28). Three blinded reviewers evaluated preoperative temporal bone CT scans to measure the distance from the labyrinthine segment of the facial nerve to the basal turn of the cochlea and attempted to predict whether or not the subject had FNS after CI.

RESULTS: In total, 32 CT scans were evaluated representing 49 ears that underwent CI.The distances (mm) measured from the labyrinthine segment of the facial nerve to the basal turn of the cochlea in both the axial (0.3 ± 0.3 versus 0.6 ± 0.3) and coronal (0.4 ± 0.2 versus 0.6 ± 0.2) orientation were significantly different between the two groups (p = 0.0001 and p = 0.0034) respectively. The intraclass correlation coefficient demonstrated good (K > 0.7) reviewer correlation in both the reviewers' measurements and predictions. The sensitivity, specificity, positive predictive value, and negative predictive value for preoperative CT scans to predict FNS were 38.5, 85.1, 19.2, and 93.8% respectively. The reviewers were 23% accurate in predicting FNS.

CONCLUSION: Based on a blinded retrospective patient-control study, CT scan measurements show a significantly reduced distance between the labyrinthine facial nerve and the basal turn of the cochlea in patients with FNS. However, it is difficult to predict who will have FNS based on these measurements.