Inner Ear Anomalies in Cochlear Implantees: Importance of Radiologic Measurements in the Classification

Objective: To classify the inner ear anomalies of cochlear implantees with profound sensorineural hearing loss. Study Design: Retrospective case review. Setting: Tertiary referral center. Patients: For the normative data of the inner ear structures, the temporal bone computed tomography of 60 patients (120 ears) with normal bone-conduction threshold (<15 dB) were used, and the data were applied to 570 ears of 285 cochlear implantees. Interventions: Predesignated inner ear structures were measured in temporal bone computed tomography images from the normal and cochlear implantation groups using a computer-based caliper that formed part of a picture archiving and communication system. Main Outcome Measures: The inner ear anomalies were defined when the structures presented visually obvious malformations or the measurements deviated 2 standard deviations from the means in the normative data. Results: The application of normative data to 570 profound SNHL ears resulted in the identification of 293 individual anomalies in 127 anomalous ears. An enlarged vestibular aqueduct was the most common individual anomaly (49 cases), followed by vestibular enlargement (38 cases) and other semicircular canal dysplasia (37 cases). When the individual anomalies were reaccounted according to the more prominent anomaly where multiple anomalies were present in each ear, incomplete partition type II was the most common (34 ears), followed by cochlear hypoplasia (22 ears) and incomplete partition type I (20 ears). Conclusion: We suggested a measurement technique for the inner ear structures using computed tomography and derived normative measurements helpful for diagnosing inner ear anomalies. Using these normative data, we classified the inner ear anomalies of profound SNHL ears in cochlear implantees.