Abstracts

2012 Audiology & neuro-otology  
Hearing impairment affects approximately 16% of the adult population and more than half of people over 60 years of age, making age-related hearing loss a major health problem. In Europe, failure to address hearing impairment costs 213 billion Euros per year (22.4 billion Euros for 16% of French adults). Hearing loss in the elderly, presbycusis, has been attributed to degeneration of cochlear sensory hair cells and/or primary auditory neurons (Shield, 2006). Presbycusis can vary in severity from
more » ... mild to severe; the more severe forms affecting communication and contributing to social isolation, depression and possibly dementia. There is a general agreement that cumulative effects of aging on hearing are exacerbated by genetic and environmental factors such as noise or drug exposure. Due to environmental noise and increasing life expectancy, the prevalence of presbycusis is expected to grow dramatically. Sound exposure during youth accelerates spiral ganglion neuron (SGN) degeneration: Based on observations of temporal bones from elderly patients, Schuknecht proposed a classification system with three major forms of agerelated hearing, namely: sensory, neural, and strial presbycusis, according to the location of damage (sensory epithelium, spiral ganglion or stria vascularis) [Schuknecht, 1993]. In the majority of cases, sensorineural hearing loss results from the loss of sensory hair cells, which in turn leads to SGN degeneration. Despite the secondary SGN degeneration, Liberman's group [Kujawa and Liberman, 2009; Lin et al., 2011] reported direct evidence showing that massive SGN degeneration can be a primary result of sound exposure, even when there is no loss of sensory hair cells. Although moderate sound exposure, in their study, pro-Audiol Neurotol 2012;17(suppl 1):3-25 4 Abstracts Conclusion: To date, only caloric restriction and the over-expression of endogenous caspase inhibitor XIAP or catalase in mice have been shown to slow down ARHL. Our results provide further evidence that targeting oxidative stress, chronic inflammation or apoptotic pathways (which have been successful following noise and ototoxic drug exposure may be efficient at preventing ARHL. Another strategy may be the modulation of autophagy, as done with rapamycin fed to extend the lifespan in the mice. Our finding that SGN degeneration shares common mechanisms with other neurodegenerative diseases (i.e., autophagic stress and protein aggregation) offers promising perspectives for the prevention of neural presbycusis. Disclosure Statement The authors state that there is no conflict of interest to be disclosed. Kujawa SG, Liberman MC: Adding insult to injury: cochlear nerve degeneration after 'temporary' noise-induced hearing loss.
doi:10.1159/000341356 pmid:22922653 fatcat:lkerurxzsvgebnx4gxlgamqyea