[Anatomy of sinus tympani].

30 temporal bones from adult cadavers of both sexes were examined. After the tympanic sinus was identified, its morphologic features were evaluated. Minimum distance from adjacent structures: lateral and posterior semicircular canal, facial nerve canal and jugular fossa were taken. Measurements were taken under operative microscope with eye-piece graduation of 0.05 mm accuracy. Four main morphologic types of entrance to the sinus and two main developmental forms--deep and shallow sinus were distinguished. Deep sinus coexisted with absence of bridge and conversely if bridge was seen sinus was shallow. Deep sinuses were located close to the facial canal, in some cases penetrating around the canal up to 2/3 of canal's circumference. This anatomical variation increase the risk of the facial nerve damage during the surgery. In most of cases tympanic sinus is oval in shape. It's long diameter lies in vertical plane. The mean distance between the sinus and adjacent structures were as following: facial nerve canal--1.5 mm, lateral semicircular canal--2.1 mm, posterior semicircular canal--1.59 mm, jugular fossa--5.5 mm. No differences dependent from gender and side were found.