Lateral Orifice of Prussak's Space Assessed With a High-Resolution Cone Beam 3-Dimensional Computed Tomography

Objectives: To describe how to obtain high-resolution computed tomography (CT) images of the en face view of the lateral orifice of Prussak's space (Ps orifice) and tympanic ring and to investigate the shape and size of these structures in normal ears and in those with chronic otitis media and attic cholesteatoma. Setting: University-affiliated referral center. Methods: Using the Accuitomo image reconstruction algorithm, the slope of the eardrum was turned to vertical on both coronal and axial images. A sagittal slice view at the eardrum gave the en face view of the eardrum. The width and height of the Ps orifice and vertical axis of the tympanic ring were measured with an automatic measuring device. Results: In the normal Ps orifice, the height is less than 1.30 mm, and the width is less than 2.63 mm. The height and width in the Ps orifice with attic cholesteatoma were significantly larger than those in normal ears and in ears with COM (p < 0.01). In the ears with COM, the width and height on average seemed larger than normal, but no significant difference was verified. The vertical axis of the tympanic ring was unaffected by the diseases. Conclusion: CT imaging of the en face view of the Ps orifice obtained by the present method is useful as an objective measure to assess bone destruction at the Ps orifice, a scutum defect, in ears with COM and attic cholesteatoma.