Atrophy of the stria vascularis is a genetically determined deafness of aging characterized by a bilateral symmetrical sensori‐neural hearing loss showing flat audiometric patterns and excellent speech discrimination. The temporal bones of individuals exhibiting this type of hearing loss were studied by serial sections and surface preparations for light microscopy and by electron microscopy. The atrophic changes are most severe in the apical regions of the cochleas and involve the marginal, intermediate and basal cells in that order of severity. It seems probable that atrophy of the stria vascularis causes some deficiency in the quality of endolymph throughout the cochlear duct, regardless of the location of the atrophy. Typically all other structures of the cochlear duct are normal, and the sense organ when stimulated within its sensitivity range is capable of normal stimulus coding, thus accounting for the usually excellent speech discrimination.

The objective of this study was to provide accurate volumetric data on the fluid spaces and soft tissue in the guinea pig inner ear by measuring all histologic serial sections by means of Metamorph Imaging Software at 400x to 1,000x magnification. The total endolymph volume of the inner ear was 4.691 mm3, of which 1.501 mm3 was in the cochlea, 3.090 mm3 in the vestibular labyrinth, and 0.100 mm3 in the endolymphatic duct and sac. The total perilymph volume was 15.938 mm3, of which 8.867 mm3 was in the cochlea and 7.071 mm3 in the vestibular labyrinth. The volume of the organ of Corti per millimeter length increased toward the apex, but the volumes of the stria vascularis, spiral ligament, and spiral limbus decreased. The volume of the macula utriculi was larger than that of the macula sacculi. The measurement of the luminal surface area of the stria vascularis was 3.944 mm2, and that of the vestibular dark cells was 5.772 mm2.

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Freshly prepared methanol saturated with sodium hydroxide and diluted 1:2 with methanol was the best solvent for removing celloidin from mouse temporal bone sections, resulting in consistent and reproducible immunostaining with the six antibodies tested.

The localization of proteins by immunostaining is a powerful method to investigate otologic disorders. However, the use of fixatives and embedding media (necessary for the preservation of morphology) can obscure antigens, making it difficult to perform immunoassays. We performed a systematic investigation of the effects of fixative and embedding medium on morphology and immunostaining of the mouse cochlea. Three different fixative solutions [4% formaldehyde (F), 4% formaldehyde + 1% acetic acid (FA), and 4% formaldehyde + 1% acetic acid + 0.1% glutaraldehyde (FGA)] and 3 different embedding media (paraffin, polyester wax, and celloidin) were used. Morphology was assessed using light microscopy. Immunostaining was studied using a panel of 6 antibodies (to prostaglandin D synthase, aquaporin 1, connective tissue growth factor, 200-kDa neurofilament, tubulin and Na⁺,K⁺-ATPase). Preservation of morphology was suboptimal with paraffin, adequate with polyester wax and superb with celloidin. Immunostaining was successful using all 6 antibodies in all 3 fixatives and all 3 embedding media. While there were differences in strength of signal and localization of antigen between the 3 fixatives, overall, FA and FGA gave the most uniform results. For a given fixative and antibody, there was surprisingly little difference in the quality of immunostaining between celloidin and paraffin, while results in polyester wax were not as good in some cases. These results suggest that celloidin may be the embedding medium of choice for both morphological and pathological studies, including immunostaining when morphology must be optimized.