Round window niche area anatomy in terms of cochlear implantation.

The round window niche area is dramatically important in terms of cochlear implantation as its individual variations influences approach to the scala tympani of the cochlea. Methods. The syntopy of round window niche area and adjacent regions was examined on 20 cadaveric temporal bones. Results and discussion. Three types of free edge of the round window niche tegmen were distinguished. In 11 specimens out of 20 well-formed free edge of the tegmen was revealed and round window membrane was fully visualized. In 6 cases a well-formed free edge of the tegmen was detected but due to the angle of this anatomic structure the membrane was only partly observed. In 3 specimens free edge of the tegmen was hypertrophic and protruded medially obscuring the membrane and the chamber of the round window niche. In 16 cases in hypotympanum area we observed a tunnel between the finiculus and fustis. This tunnel connected tympanic cavity and petrous bone cells below the cochlea. Three degrees of expression of this structure were discerned: I - 11/20 bones presented wide tunnel; II -- in 5/20 specimens only a small foramen was revealed under the finiculus; III -- in 4/20 cases this tunnel was not visualized. Learning outcome. A wide tunnel, which can be observed under the cochlea after the posterior tympanotomy, may mimic the round window niche. This can lead to the false electrode insertion. The potential risk of jugular bulb and carotid artery damage should be kept in mind as infracochlear pneumatization may serve as a pathway leading to these vessels. [ABSTRACT FROM AUTHOR]