Diagnosis of Inner Ear Malformations by Computed Tomography Measurements

Shim, Hyun Joon; Shin, Jung Eun; Chung, Jong Woo; Lee, Kwang Sun

Abstract

BACKGROUND AND OBJECTIVES: The objectives of this study were to achieve the normative measurements of inner ear structures on temporal bone computed tomography (TBCT) and, by using these data, diagnose the malformations of severe to profound sensorineural hearing loss (SNHL) ear accurately.
SUBJECTS AND METHOD
For the normative data of the inner ear structures, the TBCT 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 with severe to profound SNHL. Six identifiable inner ear structures (cochlea, vestibule, superior semicircular canal, lateral semicircular canal, posterior semicircular canal, and internal auditory canal) were measured in numerically designated areas by picture archiving and communications system. The inner ear anomalies were defined when the structures presented visually obvious malformations or when the measurements deviated 2 standard deviations (SD) from the means in the normative data.
RESULTS
We achieved the mean and SD values from the normal bone-conduction group. A total of 293 anomalies were detected in 127 of the 570 (22.3%) profound SNHL ears. An enlarged vestibular aqueduct was the most common individual anomaly (49 cases), followed by vestibular enlargement (38 cases), other semicircular canal dysplasia (37 cases), and shortened cochlea (34 cases).
CONCLUSION
We suggested a measurement technique for the inner ear structures using TBCT and derived normative measurements helpful for diagnosing inner ear anomalies. Quantitative measurements of the cochlea may improve the detection of cochlear hypoplasia and SCC dysplasia from relying on simple visual inspection.