“Cool” Research in Hearing Loss Prevention
Prevention of hearing loss is a major area of research. Novel approaches for primary and secondary prevention are in various stages of development including pharmacological and non-pharmacological approaches. Therapeutic hypothermia has been long used to protect neural and vascular integrity dating to the pioneering work of Fay nearly 75 years ago (Fay, 1940). However, systematic hypothermia can have unwanted side effects, which restricts application in clinical settings. Recently, investigators have begun to explore roles of localized therapeutic hypothermia in the prevention of hearing loss (Spankovich et al., 2016) and improved preservation of hearing and outcomes with cochlear implants (Tamames et al., 2016).
Spankovich and colleagues applied therapeutic pseudo-localized hypothermia to the prevention of cisplatin-induced hearing loss. Localized hypothermia was achieved by cooling the external ear of Guinea pigs via water irrigation (30°C). Animals were subsequently injected with a known ototoxic dose of cisplatin. The cool treatment resulted in significant decrease in hearing loss and preservation of hair cells compared to control animals that underwent ear canal irrigation with body-temperature water and a second experimental group that underwent warm treatment (44°C). Interestingly, the warm treatment groups showed increased cisplatin-induced hearing loss and hair cell loss.
Tamames et al. (2016) examined the application of direct localized therapeutic hypothermia on the trauma caused by cochlear implant insertion in rats. Localized hypothermia of 4 to 6°C was applied to the middle turn of the cochlea for 20 minutes before and after cochlear implantation via custom designed probe. They demonstrated significant protection of residual hearing and diminished the loss of hair cells compared to a normothermic control group.
Collectively, these studies suggest localized therapeutic hypothermia as potential alternative methods to prevent drug and surgical trauma to the inner ear. Further research in mechanism for protection, temperature delivery platforms, and human application are needed.
Spankovich C, Lobarinas E, Ding D, Salvi R, Le Prell CG. (2016) Assessment of thermal treatment via irrigation of external ear to reduce cisplatin-induced hearing loss. Hear Res 332:55-60.
Tamames I, King C, Bas E, Dietrich WD, Telischi F, Rajguru S. (2016) A cool approach to reducing electrode-induced trauma: Localized therapeutic hypothermia conserves residual hearing in cochlear implantation. Hear Res 339:32-39.