Inferior retrotympanum revisited: an endoscopic anatomic study.

OBJECTIVES/HYPOTHESIS To describe the inferior retrotympanic anatomy from an endoscopic perspective. STUDY DESIGN This was an anatomic study on a retrospective case series. METHODS During November 2009 and December 2009, videos from endoscopic middle ear procedures carried out between June 2007 and November 2009 and stored in our database were retrospectively reviewed. Surgeries in which the inferior retrotympanic region was visualized were included in the study. Accurate descriptions of the anatomic findings were made for each ear included in the study group. RESULTS The final study group consisted of 25 videos from 25 ear procedures. In 14/25 subjects, a bony ridge connecting the inferior portion of the styloid prominence to the anterior and inferior lip of the round window niche (Proctor's sustentaculum promontory) was identified and renamed the finiculus (from the Latin finis, -is: borderline), representing the ideal limit between the inferior retrotympanum and hypotympanum. In 14/25 patients, a complete sinus subtympanicus could be identified, lying between the subiculum and finiculus. CONCLUSIONS Endoscopic exploration of the middle ear might guarantee a very good exposure of the inferior retrotympanum, allowing detailed anatomic descriptions of this hidden area. Improvement in our knowledge of its anatomy might decrease the possibility of residual disease during cholesteatoma surgery.