Surgical anatomy of the anterior epitympanic space.

The structure of the anterior epitympanic space was examined in 16 temporal bones. The space showed three different structural types. In all three types the posterior boundary of the space was marked by a bony plate jutting downward and covered by a mucous membrane. No anterior boundary was found in type A (19%), the space being continuous to a widened eustachian tube orifice. In type B (31%), the space was anteriorly bounded by a mucosal fold that continued to the tensor tympani fold. In type C (50%), the space assumed the shape of a bulge extending into the bony structure and sealed at the bottom by the tensor fold. The ear surgeon is advised to be familiar with the structure of the anterior epitympanic space before intervening to remove cholesteatoma or create an anterior ventilation route.