Diabetes-induced cellular changes in the inner ear

Aims: literature outlining the impact of diabetes on the inner ear environment and the exact etiology of diabetes-induced hearing malfunctioning is scarce. Methods: The Scopus, Pubmed and google scholar databases were used to source relevant epidemiological, clinical, biomedical, histopathological, otolaryngological and pharmacological articles published between 1960 and 2020 using keywords ‘diabetes, hearing loss, inner ear, cellular, cochlea, microangiopathy, neuropathy’. AG and CD preidentified and reviewed selected articles to structure and construct the manuscripts based on relevant inclusion criteria of epidemiological, animal histopathological as well as human temporal bone findings in diabetes setting. Results: several histopathological findings in different animal models of diabetes have highlighted the existence of various abnormalities in their ears, compared with healthy control animals. The prevalence of such associations on the other hand has recently been observed in numerous epidemiological studies across various populations. A plethora of events associated with diabetes and dysglycaemia are linked to biochemical alterations, impaired physiological homeostasis, perturbed blood rheological characteristics and architectural disturbances in the vestibulocochlear system. While various hypotheses have been put forward to explain such associations, microvascular impairment of the inner ear vasculature as well as neuropathic involvement constitute two major ones to date. Conclusions: this review highlights associations between diabetes as a serious endocrinological manifestation and hearing impairment (an overlooked sequalae of diabetes), discusses fundamental etiologies (microangiopathy and neuropathy) of hearing dysfunction in patients with diabetes and sheds light on the otological and audiological impacts of diabetes on the inner ear environment