MALFORMATIONS, ANOMALIES, AND VESTIGIAL STRUCTURES OF THE INNER EAR

Abstract

ANOMALIES and malformations of the inner ear are uncommon. The majority of them are found either together with abnormalities of the external and middle ear, in cases of so-called congenital atresia, or, as a rule, without other malformations, in inherited nerve deafness. The latter abnormalities have been reviewed in an earlier paper (Altmann¹). The structures discussed in this paper are primarily of interest to anatomists and embryologists. Certain anomalies of the osseous capsule of the labyrinth have, however, lately aroused considerable interest among otologists because of their possible relationship to the development of otosclerotic foci. MEMBRANOUS LABYRINTH In discussing malformations of the membranous labyrinth, the phylogenetically older pars superior will be reviewed first. Variations in the mode of origin of the endolymphatic duct from the utricle and saccule (Bast²; Bast and Anson³) should be noted. In about 83% of the cases observed, the angle between the utricular