Abstract
OBJECTIVE
We describe a method to obtain a front view image of the lateral orifice of Prussak's space (Ps orifice or Pars flaccida) and tympanic ring (Pars tensa) using a high resolution cone beam CT. Using this method, measurements of these structures in normal and diseased ears are made, and the importance of the method for exact diagnosis of scutum defect is emphasized.
METHOD
Width and height of the Ps orifice and vertical axes of the tympanic ring were measured on ten normal ears, 13 ears with chronic otitis media (COM) and 18 ears with acquired attic cholesteatoma.
RESULTS
The size of the Ps orifice is said to be normal if the height is less than 1.30mm and the width less than 2.63mm. In 100% of the ears with cholesteatoma, the height of the Ps orifice was enlarged beyond the normal limit, and in 94.4% of the ears the width showed abnormal enlargement. The width and height in ears with cholesteatoma were significantly larger than those in normal ears and in ears with COM (p<0.01). As to the relationship between cholesteatoma staging and the size of Ps orifice, no close relation was seen in the width. In contrast, the height was significantly larger in the extensive cases (p<0.05, ANOVA). No significant difference was found between normal subjects and ears with COM.
CONCLUSION
To determine the indications and appropriate method of reconstruction for tympanic scute, the CT images of Ps orifice certainly provide valuable information.