Mondini's deafness. A review of histopathology.

From a histopathological survey of 12 ears (7 cases) of Mondini's deformity and deafness, the following conclusions or interpretations are drawn: 1) Mondini's bony deformity diagnosable by polytomography does not necessarily indicate Mondini's deafness or x-ray diagnosis of Mondini's deafness cannot be specifically relied upon. 2) The pars superior (semicircular canals and utricle) may be absent (aplastic) or the canals may be enlarged leading to interesting questions regarding vestibular physiology in such patients. 3) Enlarged endolymphatic duct and deficient utriculoendolymphatic valve are commonly found associated with absence of endolymphatic hydrops or collapse suggesting an operational longitudinal flow. 4) One and one-half or fewer (instead of 2 1/2) cochlear turns are characteristic; however, end-organ of Corti lesions (aplasia) may be present or absent leading to interesting speculations for further research regarding auditory function, especially in those cases with normal-appearing sensory structures. 5) Mechanisms of hearing loss in Mondini's deafness can be variably explained on the basis of inner ear or middle ear pathology including dysgenesis of the end-organs and associated neural elements sufficient to cause sensorineural hearing loss, aplasia of the oval or round windows which might explain manifest "sensorineural hearing loss" in the presence of normal-appearing organs of Corti and aplasia or infection of the middle ear causing a conductive loss which can be superimposed upon a sensorineural hearing loss.