In order to appreciate the complex embryology of the facial nerve, one has to have a basic understanding of cranial embryology as a whole. Although it may seem daunting to the casual reader, revisiting cranial embryology allows for a more comprehensive understanding of the final 3-dimensional structure of the nerve, as well as the inherent logic in its development. To this end, this article briefly discusses numerous important processes in head and neck embryology, namely the implications of patterning in hindbrain development, the diverse roles of neural crest cells, migration of the neural crest cells into the branchial arches (particularly the hyoid arch), and the genetic control of these processes. This may help prepare the otolaryngologist to comprehend and anticipate variations encountered in clinical practice, such as anticipating facial nerve anomalies in congenital stapes fixation.
However, the main objective of this article is to outline the embryology of the facial nerve and its common clinical implications. The reader is referred to Embryology and Anomalies of the Facial Nerve and Their Surgical Implications, 2nd Ed for a more comprehensive review of the development of the facial nerve and the associated development of the ear (see table 1).
The surgical anatomy and landmarks of the facial nerve.
Schematic illustration shows the facial nerve and its peripheral connections. Note the interconnections of cranial nerve (CN) VII with CN V, CN IX, and CN X.