Current Embryology of the Temporal Bone, Part II: the Middle and External Ears, the Statoacoustic and Facial Nerves, and When Things Go Developmentally Wrong

The development of the temporal bone is complex, with 3 distinctly different origins, namely, the inner ear derives from neuroectoderm, the middle ear comes from branchial arch mesoderm and endoderm, and the external ear arises from branchial ectoderm. The current understanding of how these varied structures come together to form the normal functioning ear is the basis of this review. As we now are starting to gain insight into the molecular biology that drives this complex process, some molecular information is included in this review. This molecular biology is primarily based on animal experiments and, not only provides a better understanding of how the normal anatomy develops, but provides insight into how the malformations of the temporal bone arise. The review was heavily illustrated to help the reader better understand the text. There also was a section that described the major congenital-related abnormalities that have known associated gene malfunctions.

Learning Objective: The reader will understand the development of the ear and how it can lead to the congenital variations that are encountered in a radiology practice.