Bifurcation of Facial Nerve

Introduction: Abnormal separation of CN7 much earlier in embryogenesis may be necessary for a bifurcation or trifurcation anomaly to result. Early division of the nerve at around 4-6 weeks may allow the displacement of one segment by the developing temporal bone structures.By the 8 th week, the orientation of CN7 within the temporal bone has been established, with nerve’s ultimate position and bony covering determined by development of stapes and membranous labyrinth. The basic configuration of the facial nerve is completed at around 8 weeks, whereas the mesenchymal tissue through which it passes and the structures it innervates are still poorly formed. The fibrous layers surrounding the facial nerve seem to be responsible for the final architecture of the facial canal. Aim: Knowledge of the surgical anatomy of the facial nerve and facial canal is essential in middle ear surgery. The study in full term foetuses will help in applying the facts to new born, infants and young children up to the age of 2 years. Materials & Methods: 30 fetuses were used to expose 60 fetal temporal bones. In these the petrous part was dissected, decalcified and serial sections were taken. Observation: Facial nerve bifurcation was seen in one temporal bone in its tympanic segment in the medial wall of middle ear. Discussion: Bifurcation of its intratemporal portion is a rare malformation in which focal splitting of one or more facial nerve segments occurs (Christine et al, 2003). ) In the present study bifurcation of the facial nerve was observed in the tympanic segment in the medial wall of middle ear.