Coronal computed tomography of the normal vestibular aqueduct in children and young adults.

OBJECTIVE To characterize the appearance of the normal vestibular aqueduct on coronal computed tomography (CT). DESIGN Retrospective evaluation of routine CT images of the temporal bones. SETTING Private tertiary care center. PATIENTS Twenty-four children and young adults (14 females and 10 males), aged 2 to 24 years (average age, 10 years). MAIN OUTCOMES MEASURES Axial CT images were evaluated for the size of the vestibular aqueduct as previously described. On coronal CT images the vestibular aqueduct was evaluated for shape, dimensions, and angle. These measurements were made posteriorly, at the first point of vestibular aqueduct definition, and anteriorly, where the vestibular aqueduct abuts the posterior semicircular canal. RESULTS We were able to measure the vestibular aqueduct on 100% of the anterior coronal views, 77% of the midisthmus axial CT images, and 53% of posterior coronal CT images, (P<.001). The shape of the vestibular aqueduct on coronal CT scans varied posteriorly to anteriorly from being a slit to being an oval or round. The dimensions (mean + SD) of the isthmus on the anterior coronal views were 3.1 + 1.8 mm long by 1.6 + 0.8 mm wide. The upper limits of normal, as defined by the mean + 2 SDs, are 6.8 x 3.3 mm. CONCLUSIONS We have easily and consistently identified the vestibular aqueduct on coronal CT images; in fact, we found the vestibular aqueducts more consistently measurable on coronal CT scans than on axial CT scans. The addition of these views may improve the sensitivity of the CT scan in the evaluation of sensorineural hearing loss in children.