外耳・中耳形態異常の臨床

抄録

Development of the external ear and middle ear as the organs of hearing is a complex series of events involving many tissues of different embryonic origins. The pharyngeal arches give rise to six auricular hillocks that form the major anatomic structures of the external ear. It is well known that the first branchial arch is the origin of the head of the malleus, body of the incus, and the mandible, and the derivatives of the second arch include the stapes bone, the long process of the incus, and the manubrium of the malleus. There is a spectrum of development, and the more hypoplastic the mandible, the more hypoplastic the middle ear, because of the earlier arrest in development. While dysfunction of the chorda tympani nerve was not correlated significantly with the anatomic structures of middle ear anomalies, presence of facial nerve paralysis was significantly correlated with the development of the middle ear structures. In congenital microtia, surgical correction for hearing improvement is sometimes difficult and challenging. Therefore, not only surgery, but also hearing acquisition with the aid of a device should be considered. Recently introduced devices have been shown to improve the hearing outcomes and quality of life in patients with microtia who might not otherwise benefit from traditional hearing aids. Thorough knowledge of the embryology and anatomy of the ear is essential for establishing accurate diagnosis and providing appropriate treatment.