Update on the radiological diagnosis of enlarged vestibular aqueduct (EVA) – therapeutic and prognostic implications

Objectives Enlarged vestibular aqueduct (EVA) is a common finding associated with inner ear malformation (IEM). Furthermore, EVA can indicate the presence of syndromic diseases. However, uniform radiologic definitions for EVA are missing. This study evaluates VA-volume in different types of IEM and compares 3D-reconstructed VA-volume to 2D-measurements.

Methods 98 CT datasets from temporal bones were analyzed (56 with IEM; [cochlear hypoplasia (CH;n=18), incomplete partition type I (IPI;n=12) and type II (IPII;n=11) and EVA (n=15)]; 42 controls). VA-diameter was measured in axial images. VA-volume was analyzed by 3D-reconstruction. Inter-rater-reliability (IRR) was assessed using the intra-class-correlation-coefficient (ICC).

Results Significant differences in VA-volume between patients with EVA and controls (p < 0.0001) as well as between IPII and controls (p<0.0001) were found. VA diameter at the midpoint (VA midpoint) as well as at the operculum ( VA operculum) and VA volume showed weak to very strong correlations in IPI (VA midpoint: r=0.78, VA operculum: r=0.91), in CH (VA midpoint : r=0.59, VA operculum: r=0.61), in EVA (VA midpoint: r=0.55, VA operculum: r=0.66) and in controls (VA midpoint : r=0.36, VA operculum : r=0.42). Highest IRR was found for VA volume (ICC=0.90)

Conclusion VA diameter is an unreliable estimate of VA volume since (1.) measurement of VA diameter does not correlate well with VA volume and (2.) VA diameter shows a lower IRR than VA volume. VA volumetry provides new complementary information for the diagnosis of EVA and thus the clinical prognosis. The presented data suggest VA-volumetry to improve the diagnostic workup of isolated EVA and IEM. Consequently, an implementation into the diagnostic tools is recommended.

Conflict of Interest

The author declares that there is no conflict of interest.

Publication History

Article published online:
24 May 2022