Endoscopic Anatomy of the Protympanum.

The protympanum, a final common pathway between the tympanic cavity and external environment, is gaining relevance due to the ease and completeness of visualization with angled endoscopes. Two primary conformations are described, quadrangular and triangular, and new anatomic structures such as the protiniculum, subtensor recess, and protympanic spine are defined. Surgical relevance of the protympanum is described with respect to ventilation, cholesteatoma, cerebrospinal fluid leak, otic neuralgia, and surgical access to the eustachian tube.