Long-term ototoxic effects of neomycin applied topically in the middle ear: A morphological study in the guinea pig

Abstract

Neomycin was instilled daily, uni-or bilaterally, into the middle ear of guinea pigs for three months. The cochleae were examined, by light and electron microscopy, six months after the end of treatment. The organs of Corti of the treated ears were completely destroyed, and in the most advanced lesions, were substituted by a single layer of very thin flat cells. In the spiral ganglion only some glial cells and a few neurons could be observed. All surviving neurons were myelinated, and their ultrastructure was greatly altered, with disappeared, losing it amorphous and filamentous components. The spiral limbus and the stria vascularis were atrophic and were also covered, in the final stages, by flat elongated cells. In view of its morphological characteristics, this epithelium may arise from the displacement of the interdental cells and perhaps from the cochlear surface of Reissner's membrane.

Transplantation and survival of mouse inner ear progenitor/stem cells in the organ of Corti after cochleostomy of hearing-impaired guinea pigs: preliminary results

“…Histologically, the OC and other specialized structures of the cochlear duct are usually severely injured after treatment with neomycin ( 14 , 28 ). In our study, we did not observe the complex cellular organization of the OC, including the inner and outer hair cell rows and specialized supporting cells.…”

Ototoxicity of Topical Ciprofloxacin/Dexamethasone otic Suspension in a Chinchilla Animal Model

“…An extensive body of literature exists on aminoglycoside antibiotics with virtually all studies demonstrating that, when applied topically into the middle ear space, aminoglycosides are ototoxic in experimental animals (including chinchillas). However, to date no animal study has investigated the ototoxicity of ciprofloxacin/dexamethasone eardrops 17–22 …”

Cell Division and Maintenance of Epithelial Integrity in the Deafened Auditory Epithelium

“…In animal models, pathology consisting of a "flat epithelium" in the organ of Corti may be induced drastically in severe cases of ototoxicity, 3 or progress slowly over a long time. Patients visiting the otolaryngology clinic with severe hearing loss are likely to have a flat epithelium in their inner ears.…”

“…This can occur due to an extremely severe trauma that causes direct damage to the supporting cells, or over time after a variety of less severe lesions. Specific instances include trauma caused by neomycin ototoxicity, [2][3][4] human inherited cochlear disorders such as cochleosaccular dysplasia or Usher's syndrome 5 and human cochlear infectious disease such as congenital syphilis. 6 When the differentiated supporting cells are absent, the basilar membrane is covered by a layer of flat or cuboidal simple epithelial cells, which we define as the "flat epithelium".…”