A possible role of inner ear melanocytes in tinnitus and audiovestibular disorders

Melanocytes are present in the skin and hair follicles, as well as in the eye, the leptomeninges, the anal canal and the inner ear. In the inner ear melanocytes are found both in the intermediate layer of the stria vascularis of the cochlea and in the dark cells of the vestibular organs. They are believed to play an important role in the production of endolymphatic potentials and in the maintenance of normal volumes of the inner ear fluids. Melanocytes disorders have been associated to some audiological abnormalities such as the Waardenburg syndrome and/or the Vogt-Kayanagi-Harada syndrome, characterized by both hearing impairment and pigmentation abnormalities. We propose that melanocytes could potentially be involved with inner ear fluid pressure dysfunction influencing conditions such as endolymphatic hydrops and Ménière’s disease. Recently, we reported the case of a patient in whom the appearance of a choroidal melanoma coincided with the exacerbation of tinnitus and vertigo spells in a unilateral Ménière’s disease that had been clinically silent for more than ten years. The symptoms disappeared after the radiotherapy treatment and did not show up again during the following three years. We suggest that inner ear melanocytes could be a target of an autoimmune process in patients affected by melanoma as well retinal melanocytes in melanoma-associated retinopathy. The immune system could produce antibodies that cross-react with both the melanoma cells and the labyrinth melanocytes, causing an altered homeostasis of endolymphatic liquids. In this perspective, audiovestibular disorders could be interpreted as an attempt by the individual immune system to develop anti-tumoral response. Autoimmune processes affecting inner ear melanocytes could be considered as a potential cause of tinnitus and audiovestibular disorders.