Bony anatomy of the anterior epitympanic space.

The anatomy of the anterior epitympanic space is complex and relatively unfamiliar to the surgeon. The size of the space is unpredictable. From the surgeon's perspective, we studied the bony anatomy of the anterior epitympanic space in 35 cadavers. There was an impressive variability of bony openness into the anterior mesotympanum; the openness was bilaterally symmetrical. As a potential auxiliary ventilation route for the epitympanum of the chronic otitis patient, each specimen was found to have sufficient room to surgically establish a route at least 2 mm in diameter to connect with the anterior mesotympanum. None of the specimens had dehiscent facial nerve in the anterior epitympanic space, but 60% of specimens had dehiscent facial nerve adjacent to the stapes. The anatomic variations of the anterior epitympanic space were not related to prior otitis media. Three fourths of the medial walls of the anterior epitympanic spaces lacked the bony trabeculae that are otherwise typical of the epitympanum. Because the medial wall contours were bilaterally symmetrical, because the contours were unassociated with indicators of prior otitis media, and because of apparent contour differences in Orientals and Caucasians, a congenital factor is suggested to determine the contour of the medial wall of the anterior epitympanic space.