A New Methodology for Evaluation of Large Vestibular Aqueduct in CT and MRI Images.

HYPOTHESIS: Development of a new method for large vestibular aqueduct (LVA)/large endolymphatic sac anomaly (LESA) assessment using magnetic resonance imaging (MRI) and computed tomography (CT)/cone beam CT (CBCT) images. The secondary objective was to compare both modalities.

BACKGROUND: The gold standard for LVA diagnosis is the analysis of CT images using Valvassori and Clemis or Cincinnati criteria. The previous studies showed inconclusive results regarding the correlation between audiological and radiological data.

METHODS: Retrospective analysis of radiological images from 173 patients (315 ears), who were diagnosed with LVA/LESA based on CT/CBCT and/or MRI images of the temporal bone. The images obtained using both techniques were used to measure the following dimensions of vestibular aqueduct (VA)/endolymphatic duct (ED)/intraosseous endolymphatic sac (ES): width of the opening, length, and width at external aperture. In MRI images, the maximal contact diameters of the extraosseous or intraosseous ES and dura mater were measured as well.

RESULTS: LVA has been reported to be bilateral in 82% (142 patients) and unilateral in 18% (31 patients) of cases. Comparison of MRI and CT/CBCT measurements showed a moderate correlation (0.64) in external aperture, a moderate correlation (0.57) in the width of the VA opening, and a weak correlation (0.34) in length measurements (p < 0.05).

CONCLUSION: We developed a new method to identify the heterogeneous pathology of LVA/LESA using reconstruction along the VA/ED/intraosseous ES axis, three measurements on two planes, and focus on the maximal contact diameter between the extraosseous or intraosseous ES and dura mater.