Abstract: To measure structures of the posterior tympanum and thus to provide theoretical reference for operation approach related to the middle ear. Methods60 sides of 30 dry temporal bone specimens had their mastoids outlined by an electric drill, and then the related structure of the posterior tympanum was exposed. Distances of the related anatomic structures were determined under surgical microscopy. ResultsDistances between pyramidal eminence and chordal eminence and the facial canal were 3.22±0.41mm and 3.59±0.48mm, and length of the tympanic chorda posterior tubules was 9.44±1.65mm. Distances between pyramid segment of the facial canal and chordal eminence, lateral semicircular canal and posterior semicircular canal were 3.34mm±0.42mm, 1.54±0.25mm and 2.15±0.29mm, respectively. The vertical segment of the facial nerve went down on the convex arc and vertically went down only in 2 cases (3.3±3%). The musculus stapedius all passed through the front wall of the facial nerve. The tympanic chorda nerve came from the facial nerve, outside the canal in 9 cases(15%), from the inferior one-third in 49 cases (81.67%), and from the middle one-third in 2 cases (3.33%). ConclusionWhen the facial recess is opened, distance from the chordal eminence to the pyramid segment and the pyramidal eminence can be regarded as the width of the facial recess. The pyramidal eminence and the facial canal are regarded as the basis for searching for each other. Pyramidal eminence and chordal eminence should not be lowly abraded in order to avoid damaging the musculus stapedius and chorda tympani nerve when dealing with a facial recess lesion.

Key words: Applied anatomy, Facial recess, Posterior tympanum, Facial nerve