Vitamin A-induced ear malformations in rats as a model for analysis of atresia auris congenita: a microsurgical and histological study.

Abstract

Teratogenic damage was induced in pregnant Wistar rats with an overdose of vitamin A to clarify the genesis of the atresia plate, the behavior of the facial nerve, and the rotation of the middle ear. Results suggested that contradictory statements in the literature concerning the atresia plate could be explained in the following way: the plate does not arise from a single branchial arch. The os tympanicum, the pars squamosa of the temporal bone, and the hyperplastic labyrinthine capsule share in its formation. Findings similar to the human atresia auris congenita, such as malformation of the auricle, atresia of the external ear canal, and changes in the ossicles and lumen of the middle ear space, were obtained. A cranial and labyrinthine dysmorphia leads to rotation of the middle ear and a walling-in of the facial nerve, which explains its functional disturbance. Extreme variations in the course of the facial nerve were not found. In 62 cases of severe human ear malformation, the operative findings corresponded to the experimentally produced ear malformations.