[Morphometric study of the mastoid segment of the facial nerve].

OBJECTIVE Our study emphasizes the relationship between the temporal bone structures and the mastoid portion of the facial nerve. MATERIAL AND METHODS Thirty-two temporal bones taken from adult cadavers of both sexes subjected to tympanoplastic procedure were used to make reference measures of the mastoid portion of the facial nerve. Appropriate instruments were used for measurement and statistic analysis was subsequently performed. RESULTS The digastric ridge presented a positive correlation with the stylomastoid foramen in comparison with the sigmoid sinus (P=.03). There was a correlation between the position of the short apophysis of the incus and the position of the facial nerve (P=.001). The distance from the sigmoid sinus to the mastoid portion of the facial nerve presents a positive linear relationship throughout its length (P< .001). The tympanic membrane presented a positional correlation with the distal portion of the facial nerve (P< .008). CONCLUSIONS The mastoid portion of the facial nerve is proportional to reference structures in the temporal bone and this may help us to define measures prior to surgical otologic procedures.