Hearing preservation surgery: From animal research to clinical application

Abstract

Disabling hearing loss is an important health issue worldwide. Exact numbers of hearing disability are not available for the Netherlands. In 2011 about 800.000 people visited the general practice because of hearing loss, which is thought to be an underestimation (Gommer et al., 2013). For specific subpopulations, i.e. adolescents and elderly, this number is estimated to grow. There are indications that the prevalence of noise induced hearing loss increases in adolescents due to the increased exposure to potentially damaging sound levels (Shargorodsky et al., 2010). Also, the prevalence of age related SNHL is expected to increase due to aging (due to both an increase of the percentage of elderly in the population and the increase of life expectancy). Annually, ~450 patients with severe to profound SNHL receive a cochlear implant in the Netherlands. This number is expected to grow the following years. Due to a generally improving hearing performance of CI users, the criteria for cochlear implantation are expanded. Patients with a substantial degree of residual hearing are implanted nowadays. Protection of cochlear structures is regarded of general importance, for both CI recipients with or without residual hearing, with as goal to improve cochlear implant hearing performance. Therefore, much attention is given to optimize surgical strategies. Some of these strategies are common clinical practice and are assumed to improve the outcome in cochlear implant patients. In this thesis we investigated the effect of some of these strategies on a biological level (protection of the auditory nerve in guinea pigs) and a clinical level (residual hearing outcome and hearing performance in cochlear implant patients). On the one hand, this thesis looks back and evaluates outcome variables in patients, thereby contributing to a scientific basis of the best clinical practice. On the other hand, animal research providing more insight on the actual effect of treatments on the auditory nerve contributes to improvement of current strategies used in patients and the development of clinical applications in the future.