The biomechanical characteristics of human vestibular aqueduct: a numerical-based model construction and simulation

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.

Analysis of the vestibular aqueduct development on the risk for suffering from idiopathic sudden sensorineural hearing loss

OBJECTIVE

Large vestibular aqueduct syndrome (LVAS) is one of the etiology of hearing loss. Clinically, we observed that the VA size of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) did not meet the diagnostic criteria of VA enlargement, but there were individual variations. Through this study, we want to understand the VA development and explore its risk for suffering from ISSNHL.

METHODS

74 patients with ISSNHL were retrospectively reviewed in our department from June 2018 to September 2021. Meanwhile, 57 people with no ear diseases were randomly selected as the control group. All their clinical information were systematically collected. The axial thin-slice CT images of temporal bone were used to observe and measure the VA in ISSNHL and controls. ISSNHL were classified as different types and grades according to pure tone audiometry and the degree of hearing loss, respectively. Logistic regression analysis was adopted to evaluate the risk factors of different types and grades of ISSNHL.

RESULTS

The operculum morphology could be funnel-shaped, tubular and invisible, but they had no statistical difference in the morbidity of ISSNHL. The operculum width of the affected sides in the case group was significantly wider than that of the matched sides in the control group (0.84±0.35mm vs 0.68±0.34mm, p=0.009), but the midpoint width had no statistical difference (p=0.447). The operculum width was an independent risk factor for the total hearing loss type (p=0.036, OR=4.49, 95% CI=1.10-18.29), moderate (p=0.013, OR=17.62, 95% CI=1.82-170.95) and profound (p=0.031, OR=4.50, 95% CI=1.14-17.67) grade of ISSNHL. Hypertension was an independent risk factor for the severe grade (p=0.004, OR=12.44, 95% CI=2.19-70.64) of ISSNHL. Both the operculum width (p=0.048, OR=7.14, 95% CI=1.02-50.26) and hypertension (p=0.014, OR=6.73, 95% CI=1.46-30.97) were the risk factors for the flat type of ISSNHL. The midpoint width of the VA, gender, age, diabetes mellitus, hyperlipidemia, and plasma fibrinogen concentration had no significant effect on the risk for suffering from ISSNHL.

CONCLUSION

The development of the VA operculum is a risk factor for some types and grades of ISSNHL. Hypertension remained a risk factor for ISSNHL.

Normal Enhancement within the Vestibular Aqueduct: An Anatomic Review with High-Resolution MRI

BACKGROUND AND PURPOSE

The normal appearance of the vestibular aqueduct on postcontrast MR images has not been adequately described in the literature. This study set out to characterize the expected appearance of the vestibular aqueduct, with particular emphasis on the enhancement of the structure on both 3D FSE T1 and 3D-FLAIR sequences.

MATERIALS AND METHODS

All MR imaging examinations of the internal auditory canals performed between March 1, 2021, and May 20, 2021, were retrospectively reviewed. All studies included high-resolution (≤0.5-mm section thickness) pre- and postgadolinium 3D FSE T1 with fat-saturated and postgadolinium 3D-FLAIR sequences. Two neuroradiologists independently reviewed the MR images of the vestibular aqueduct for the presence or absence of enhancement on both T1 and FLAIR images and compared the relative intensity of enhancement between sequences. The presence or absence of an enlarged vestibular aqueduct was also noted.

RESULTS

Ninety-five patients made up the patient cohort, of whom 5 did not have postcontrast FLAIR images available (50 women [55.6%]). On both sides, enhancement was significantly more commonly seen on postgadolinium FLAIR (76/180, 42.2%) than on T1 fat-saturated images (41/190, 21.6%) (P < .001). The intensity of enhancement was significantly greater on postgadolinium FLAIR images than on T1 fat-saturated images (38.9% versus 3.7%, respectively; P < .001).

CONCLUSIONS

Enhancement within the vestibular aqueduct is an expected finding on MR imaging and is both more common and more intense on postgadolinium 3D-FLAIR than on T1 fat-saturated sequences. Such enhancement should not be confused with pathology on MR imaging unless other suspicious findings are present.