Conductive hearing loss in large vestibular aqueduct syndrome -clinical observations and proof-of-concept predictive modeling by a biomechanical approach

Predictive accuracy of wideband absorbance in children with large vestibular aqueduct syndrome: A single-center retrospective study

Objectives

This study aimed to assess the clinical significance of Wideband Absorbance (WBA) in children with Large Vestibular Aqueduct Syndrome (LVAS), which could potentially serve as diagnostic and predictive markers for LVAS in children.

Design

This was a single-center retrospective case-control study. Audiological measurements and Wideband Acoustic Immittance (WAI) were performed. Propensity score matching (PSM) was considered to treat group imbalance. The Receiver Operating Characteristic (ROC) curves and area under the ROC curve (AUC) were used to evaluate the sensitivity and specificity of WBA.

Study sample

Participants included 42 children with LVAS and 163 normal children aged 6 months -11 years recruited from clinical audiology settings between 2019 and 2021.

Results

The WBA at Tympanometric Peak Pressure (WBATPP) and Ambient Pressure (WBAA) in the LVAS group were significantly lower than those of the control group at 1259-2000 Hz but higher at 4000-6349 Hz (p < 0.05, power >0.8). The WBAA (1587 Hz) AUC value was 0.805, identifying a score ≤0.565 as indicative of a LVAS risk.

Conclusions

WBA holds promise in distinguishing LVAS from the normal condition and warrants further exploration as a tool to examine the influence of inner ear pressure on acoustic energy transmission in the middle ear.

Insidious Cases of Enlarged Vestibular Aqueduct (EVA) Syndrome Resembling Otosclerosis: Clinical Features for Differential Diagnosis and the Role of High-Resolution Computed Tomography in the Pre-Operative Setting

BACKGROUND

Enlarged vestibular aqueduct (EVA) syndrome can mimic otosclerosis in adults, presenting with an air-bone gap (ABG) and even absent stapedial reflexes. The ABG in inner-ear disorders is currently the object of several authors' studies and seems to be related to a third mobile window (TMW) phenomenon. This can lead to misdiagnosis and inappropriate treatment. Given that it would be inappropriate and harmful to perform CT scans in all patients with a clinical diagnosis of otosclerosis, this study aims to highlight some clinical features useful for the differential diagnosis between otosclerosis and these rare cases of EVA presenting with an ABG, thus enabling the identification of suspected cases to be tested with CT scans.

METHODS

Between April and May 2024, a narrative review was conducted focusing on the differential diagnosis between some rare cases of EVA and otosclerosis. Clinical, audiological, and radiologic features of both conditions were investigated.

RESULTS

This review demonstrates the diagnostic challenge in differentiating atypical cases of EVA from otosclerosis in a subset of patients. Clinical and audiological features are important for differential diagnosis, but may not always be sufficient. Therefore, high-resolution computed tomography (HRCT) of the temporal bone plays a pivotal role in definitive diagnosis.

CONCLUSIONS

In some specific cases, pre-operative imaging assessment using HRCT emerges as an essential tool for differentiating these two conditions and avoiding unnecessary stapes surgery.

A novel intronic variant causing aberrant splicing identified in two deaf Chinese siblings with enlarged vestibular aqueducts

OBJECTIVE

We aimed to evaluate the genotype-phenotype relationship in two Chinese family members with enlarged vestibular aqueduct (EVA).

METHODS

We collected blood samples and clinical data from each pedigree family member. Genomic DNA was isolated from peripheral leukocytes using standard methods. Targeted next-generation sequencing and Sanger sequencing were performed to find the pathogenic mutation in this family. Minigene assays were used to verify whether the novel intronic mutation SLC26A4c.765+4A>G influenced mRNA splicing.

RESULTS

Hearing loss in the patients with EVA was diagnosed using auditory tests and imaging examinations. Two pathogenic mutations, c.765+4A>G and c.919-2A>G were detected in SLC26A4. In vitro minigene analysis confirmed that c.765+4A>G variant could cause aberrant splicing, resulting in skipping over exon 6.

CONCLUSIONS

The SLC26A4c.765+4A>G mutation is the causative variant in the Chinese family with EVA. Particular attention should be paid to intronic variants.

A Large Vestibular Aqueduct With Conductive Hearing Loss as the Only Manifestation

Conductive hearing loss is a common clinical condition caused by disorders of the middle and external ear. Here, we report a case of conductive hearing loss with complete tympanic membranes. Clinical examinations revealed no external and middle ear lesions, but high-resolution temporal bone computed tomography revealed enlarged vestibular aqueducts. Detailed audiological tests and follow-up results indicate that the exclusive air-bone gap is the outcome of inner ear malformation but not middle ear lesions, preventing the need for tympanic assessment.

Fluid-solid coupling model and biological features of large vestibular aqueduct syndrome

Objective: Computed tomography (CT) images of the temporal bone of large vestibular aqueduct syndrome (LVAS) patients were used to establish 3D numerical models based on the structure of the inner ear, which are, in turn, used to construct inner ear fluid-solid coupling models. The physiological features and pathophysiology of LVAS were analyzed from a biomechanical perspective using finite element analysis. Methods: CT images of the temporal bone were collected from five children attending the Second Hospital of Dalian Medical University in 2022. The CT images were used to build 3D models of the inner ear containing the vestibular aqueduct (VA) by Mimics and Geomagic software, and round window membrane models and fluid-solid coupling models were built by ANSYS software to perform fluid-solid coupling analysis. Results: By applying different pressure loads, the deformation of the round window membranes occurred, and their trend was basically the same as that of the load. The deformation and stress of the round window membranes increased with the increase in load. Under the same load, the deformation and stress of the round window membranes increased with the expansion of the midpoint width of the VA. Conclusion: CT images of the temporal bone used clinically could establish a complete 3D numerical model of the inner ear containing VA. Fluctuations in cerebrospinal fluid pressure could affect inner ear pressure, and VA had a limiting effect on the pressure from cerebrospinal fluid. The larger the VA, the smaller the limiting effect on the pressure.