ABSTRACT
OBJECTIVES: This study aims to describe anatomical variations in the posterior tympanum. Different configurations which influence surgical decisions in middle ear surgery are described. Surgical access to the sinus tympani remains a challenge for otologic surgeons. Usually, the retrotympanum is approached through the middle ear in the anterior-posterior direction during chronic ear surgery. An endoscopic approach is necessary to detail all reliefs of the middle ear and control the total removal in a cholesteatoma surgery. MATERIALS AND METHODS: Our study included 120 ears with otosclerosis that were operated on. We have performed an intra-operative endoscopic examination with different endoscopes from the Storz company (3.0 mm diameter 45 and 70 degrees). Its rigid endoscopes have been used to obtain a detailed inspection of the entire middle ear cavity. Three main anatomical configurations increase difficulty for the otologic surgeons. RESULTS: One hundred and twenty ears were included in this retrospective study. We described 44 shallow sinus tympani of type I (36.6%), and 46 intermediary sinus tympani of type II which account for 38.4% of the ears. In these two groups, a disease such as cholesteatoma is quite easy to control. In 30 ears we observed a deep sinus tympani of type III (25%). This type of sinus is a real difficulty for the surgeon, which means that a total exploration without an endoscope is not possible and entails intraoperative risks. Some anatomical variations were noted: indeed, six high jugular bulbs were described in the middle ear (5%). In 4 other ears (3.3%), there was a posterior extension which passes under the pyramidal eminence and the fallopian canal. CONCLUSION: For 8.3% of the ears, some important intraoperative risks are involved, which can cause damage to the facial nerve or the jugular bulb. Moreover a quarter of the ears have deep sinus tympani which can not be explored with a microscope. This makes the endoscope an essential complement to the microscope in otologic surgery.
