Normative Treatment And Measurement Of Vestibular Aqueduct On HRCT Imagings To Aid The Diagnosis Of LVAS

Objective:To reconstruct the standard section of vestibular aqueduct (VA) by using multi-planar reformation (MPR) of high resolution computed tomography (HRCT). The middle width of vestibular aqueduct on standard section images was measured , and the range of normal values (99% confidence level) of which was established . The value of the middle width of vestibular aqueduct on standard section images of the temporal bone was evaluated in the patients with LVAS.Materials and methods:1. HRCT images of temporal bone were undergone in 100 cases (200 ears) with normal hearing. The standard section MPR images of vestibular aqueduct were reformatted in all cases (two sides). The detection rate of the vestibular aqueduct long limb on standard section MPR images was calculated. The middle width of vestibular aqueduct long limb on standard section MPR images was measured in all cases. The range of normal values (99% confidence level) was established. All cases were divided into male and female groups, left and right groups. Statistic analysis of the difference between the two groups was done.2. The middle diameter of vestibular aqueduct long limb was measured on standard section MPR images in the patients with LVAS. Statistic analysis between the normal and abnormal groups was done.Results:1. The vestibular aqueduct long limb was detected on axial and standard section MPR images in 198 ears, while not detected in all sections in 2 ears. On standard section MPR images, the whole long limb of vestibular aqueduct can be detected on a single image in 198 ears, while no one can be detected on a single image on the axial images.2. No difference of the value of the middle diameter of vestibular aqueduct long limb can be seen between male and female groups. No difference of the value of the middle diameter of vestibular aqueduct long limb can be seen between left and right groups.3. The value of the middle diameter of vestibular aqueduct long limb on standard section MPR images was calculated( two sides): right 0.920±0.209mm, left 0.930±0.265mm; the range of normal values (99% confidence level): right 0.2719-1.1494mm. left 0.2669-1.2411mm.4. Significant difference was detected between normal and abnormal groups about the value of the middle diameter of vestibular aqueduct long limb on standard section MPR images. (P<0.05).Conclusion:1. The long limb of the vestibular aqueduct can be detected on a single image on standard section MPR images;2. The enlargement of vestibular aqueduct can be determined when the width of the middle diameter of vestibular aqueduct long limb is greater than 1.3 mm on standard section MPR images. The diagnosis of LVAS can be made when the patients with typical clinic symptom and sign and abnormal gene test.