The round window region and contiguous areas: endoscopic anatomy and surgical implications

The round window region is a critical area of the middle ear; the aim of this paper is to describe its anatomy from an endoscopic perspective, emphasizing some structures, the knowledge of which could have important implications during surgery, as well as to evaluate what involvement cholesteatoma may have with these structures. Retrospective review of video recordings of endoscopic ear surgeries and retrospective database review were conducted in Tertiary university referral center. Videos from endoscopic middle ear procedures carried out between June 2010 and September 2012 and stored in a shared database were reviewed retrospectively. Surgeries in which an endoscopic magnification of the round window region and the inferior retrotympanum area was performed intraoperatively were included in the study. Involvement by cholesteatoma of those regions was also documented based on information obtained from the surgical database. Conformation of the tegmen of the round window niche may influence the surgical view of round window membrane. A structure connecting the round window area to the petrous apex, named the subcochlear canaliculus, is described. Cholesteatoma can invade the round window areas in some patients. Endoscopic approaches can guarantee a very detailed view and allow the exploration of the round window region. Exact anatomical knowledge of this region can have important advantages during surgery, since some pathology can invade inside cavities or tunnels otherwise not seen by instrumentation that produces a straight-line view (e.g. microscope).