Hereditary inner-ear abnormalities in animals. Relationships with human abnormalities.

A classification scheme for inner-ear abnormalities is defined, based on animals with hereditary inner-ear defects. Three major groups are (1) morphogenetic abnormalities, involving gross structural deformities of the labyrinth; (2) neuroepithelial abnormalities, in which there appears to be a primary organ of Corti defect and Reissner's membrane remains in its normal position; and (3) cochleosaccular abnormalities, showing collapse of Reissner's membranes and restriction of vestibular abnormalities to the saccule. Recent experimental findings in hearing-impaired animal mutants are taken into account. The relevance of the classification of scheme to conditions in humans is discussed. It is suggested that the Mondini and Michel deformities in humans are best considered together in the morphogenetic group. Some cases of inner-ear abnormality in humans might be considered as belonging to the neuroepithelial group.