Morphometric properties of the facial nerve in fetal temporal bones

Objectives The main aim of the study was to examine the development and course of the facial nerve within fetal temporal bones from an anatomical and neuro-otological perspective. Methods The study was conducted on 32 temporal bones from obtained fetuses (7 females, 9 male), on a mean gestational age of 26.75 ± 4.36 (range, 20–34) weeks from the collection of the Anatomy Department of Medicine Faculty. All the measurements were collected with a digital image analysis software. Results Neither male/female nor right/left significant differences were observed in relation with the algebraic data of the segment lengths and angles of the facial nerve (p > 0.05). Linear functions for meatal, labyrinthine, tympanic, and mastoid segment lengths of the facial nerve were calculated as: y = −1.206 + 0.200 × Age (weeks), y = −1.868 + 0.153 × Age (weeks), y = −2.327 + 0.325 × Age (weeks), and y = −1.507 + 0.246 × Age (weeks), respectively. In addition, linear functions for first and second genu angles were calculated as: y = 105.475–0.117 × Age (weeks) and y = 140.446–0.042 × Age (weeks), respectively. Conclusion The regression equations and the scatter plot with increment curve, representing the growth dynamics of the facial nerve can be used for estimating its lengths and for understanding its development. The data suggest that there is a dramatic change transition from fetal life to the gathered data of adulthood in the length of meatal and mastoid segments as well as in the second genu angle; in addition, there is a partial change in the length of labyrinthine and tympanic segments as well as in the first genu angle.