Cochlear Implantation: The Volumetric Measurement of Vestibular Aqueduct and Gusher Prediction

Abstract

This study aimed to validate the role of 3D segmentation in measuring the volume of the vestibular aqueduct (VAD), and the inner ear, and to study the correlation between VAD volume and VAD linear measurements at the midpoint and operculum. The correlation with other cochlear metrics was also studied. We retrospectively recruited 21 children (42 ears) diagnosed with Mondini dysplasia (MD) plus enlarged vestibular aqueduct (EVA) from 2009 to 2021 and who underwent cochlear implantation (CI). Patients' sociodemographic data were collected, and linear cochlear metrics were measured using Otoplan. Vestibular aqueduct width and vestibular aqueduct and inner ear volumes were measured by two independent neuro-otologists using 3D segmentation software (version 4.11.20210226) and high-resolution CT. We also conducted a regression analysis to determine the association between these variables and CT VAD and inner ear volumes. Among the 33 cochlear implanted ears, 13 ears had a gusher (39.4%). Regarding CT inner ear volume, we found that gender, age, A-value, and VAD at the operculum were statistically significant (p-Value = 0.003, <0.001, 0.031, and 0.027, respectively) by regression analysis. Moreover, we found that Age, H value, VAD at the midpoint, and VAD at the operculum were significant predictors of CT VAD volume (p-Value < 0.04). Finally, gender (OR: 0.092; 95%CI: 0.009-0.982; p-Value = 0.048) and VAD at the midpoint (OR: 0.106; 95%CI: 0.015-0.735; p-Value = 0.023) were significant predictors of gusher risk. Patients' gusher risk was significantly differentiated by gender and VAD width at the midpoint.

Keywords: Mondini dysplasia; cochlear implantation; cochlear metrics; enlarged vestibular aqueduct.

Figure 1

Illustration of measurements of VAD width, 3D segmentation of VAD and inner ear, and linear cochlear metrics measurements. (A) Left Axial CT image of temporal bone showing the method for measuring VA midpoint width, (B) the method for measuring VA opercular width. (C,D) showing the 3D segmentation of the inner ear and EVA. (E–G) showing cochlear metrics using OTOPLAN^® software.

Figure 2

Descriptive characteristics of the study cohort. (A) Descriptive Statistics of the whole population (N = 42) by side of the ear (described as mean ± SD, Minimum, and Maximum, (B) Baseline characteristics for Cochlear Implanted ears (N = 33) by side of the ear, (C) Descriptive Statistics of the whole population (N = 42) by sex (described as mean ± SD, Minimum, and Maximum, (D) Baseline characteristics for Cochlear Implanted ears (N = 33) by sex, (E) Descriptive statistics of Cochlear implantation patients’ ears by Gusher outcomes, *: Significant p-Value (p ≤ 0.05), **: Significant p-Value (p ≤ 0.01), ***: Significant p-Value (p ≤ 0.001), ns: nonsignificant p-Value (p > 0.05), CDL: cochlear duct length, OC: organ of corti, VADm: vestibular aqueduct width at the midpoint, VADo: vestibular aqueduct width at the operculum). Male is colored light blue, Female is colored pink, Right is colored red, Left is colored dark blue, Gusher is colored dark green, and No gusher is colored light green.