[The behavior of the facial nerve in vitamin A and thalidomide induced atresia auris congenita. A microsurgical and histological animal study (author's transl)].

Atresia auris congenita may include either a complete or incomplete paralysis of the facial nerve as well as a possible abnormal course of its tympanic segment. Pregnant Wistar rats were given high doses (50,000, 80,000 or 100,000 USP units) of vitamin A and (10,15 or 20 mg) Thalidomide on the 8th, 9th, 10th and 11th days of gestation. The animals were then sacrificed, and the temporal bones and the medulla oblongatas of the fetuses and the adult rats were examined microsurgically and histologically. In contrast to previous reports in the literature, no significantly abnormal courses of the nerve could be found. These findings corresponded to those of 62 endaurally operated human ear malformations. The paralysis of the facial nerve in these patients seems due to a reduced diameter of the nerve and not to a malformation of its nucleus.