External Ear Aural Atresia

Aural atresia is the absence of the external auditory canal, which may be either acquired or congenital. Acquired aural atresia most often results from inflammation, trauma, radiation therapy, or otologic surgery. Congenital aural atresia is a malformation of the external auditory canal that typically causes profound conductive hearing loss in the newborn and may persist into later life. In congenital aural atresia, the middle ear structures may develop normally or have concurrent malformations.  The ear is divided into 3 parts: the inner ear, the middle ear, and the external ear. The external ear consists of the auricle (or pinna) and the external auditory canal. The external ear guides sound waves to the tympanic membrane and middle ear. However, hearing can be normal even without the pinna. The pinna also provides structural support for hearing aids and eyeglasses, if required.  Embryologically, the external ear develops from the first pharyngeal cleft and the first and second pharyngeal arches. The external ear develops from the 6 hillocks of His, and remnants of these embryonic structures can persist postnatally as cysts or fistulae that may become infected. Thus, impaired integration of these structures in utero leads to external ear malformation and conductive hearing loss. The degree of malformation varies from stenosis (<4 mm in diameter) to complete atresia of the ear canals. This malformation commonly occurs in conjunction with microtia, a condition characterized by the malformation of the auricle; rarely does this condition present bilaterally as part of a syndrome. The Jahrsdoerfer grading scale is widely used to determine surgical candidacy and predict outcomes for these patients.