Unilateral endolymphatic hydrops and associated abnormalities.

A case of unilateral endolymphatic hydrops is presented in which several significant histopathological findings are observed in the affected inner ear and are absent in the opposite ear. Moderate endolymphatic hydrops is present in all cochlear turns on the involved side. Atrophic changes in the cochlear and vestibular end-organs, partial collapse and infolding of Reissner's and the saccular membranes, and collapse of the posterior canal membrane are also seen. There is also marked narrowing of the proximal rugose portion of the endolymphatic sac, associated with a flattened, epithelial lining, dense fibrotic connective tissue, brown pigment deposition, and poor vascularity in a relatively narrowed and straightened vestibular aqueduct. Fibrosis, loss of vascularity, and brown pigment deposition are also observed in the bony channels surrounding the vestibular aqueduct.