Volumetry improves the assessment of the vestibular aqueduct size in inner ear malformation

An enlarged vestibular aqueduct (EVA) may occur in inner ear malformation (IEM). In this study, the volume of the vestibular aqueduct (VA) in different IEM is investigated and compared with 2D measurements. 98 high-resolution CT (HRCT) scans of temporal bones with IEM were analyzed (n=56; [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 by axial CT and VA volume was analyzed by software-assisted segmentation and 3D reconstruction. Differences in VA volume between groups and associations between VA volume and VA diameter were examined. Inter-rater reliability (IRR) was assessed using the intraclass correlation coefficient (ICC). Larger VA volumes were observed in IOM compared with controls. Significant differences in VA volume were found between patients with EVA and controls (p<0.001) and between IPII and controls (p<0.001). VA diameter at the midpoint (VA-mid) and at the operculum (VA-Op) correlated with VA volume in IPI (VA-mid: r = 0.78, VA-Op: r = 0.91), in CH (VA-mid: r = 0.59, VA-Op: r = 0.61), in EVA (VA-mid: r = 0.55, VA-Op: r = 0.66), and in controls (VA-mid: r = 0.36, VA-Op: r = 0.42). The highest IRR was found for VA volume (ICC = 0.90). VA diameter may be an inadequate estimate of VA volume because VA diameter measurement does not reliably correlate with VA volume and VA diameter has a lower IRR than VA volume. 3D reconstruction and VA volumetry may provide additional information in the diagnosis of EVA in cases with or without additional IEM.

Publication History

Article published online:
12 May 2023