Our understanding of noise-induced hearing loss and the indicators of hearing loss have expanded in recent years. Most significantly, recent work by researchers at the Harvard Medical School demonstrates that nerve fibers in the inner ear are even more susceptible to damage from loud noise than hair cells. Most previous research on hearing loss focused on how the loss of hair cells affects hearing. With these new findings come new avenues for therapy and new opportunities for improved public health policies.
Sound waves transmit through bones in the ear, causing vibrations to translate to electrical pulses in the fibers of the cochlear nerve. This information travels to the brain, where it is then processed. Until recently, researchers did not fully appreciate that cochlear nerve loss occurs without affecting a person’s ability to detect tone in quiet. Since tone detection in quiet is a baseline component of hearing tests, most auditory specialists using the threshold audiogram test fail to recognize some inner ear nerve damage.
Current federal noise exposure guidelines posit that transient threshold elevation levels are not harmful to the ear. However, we now know that even transient elevations cause nerve damage, which can lead to later hearing issues. Sharing this information and encouraging people to protect their ears can reduce the risk for future hearing impairment.
Researchers understand that the death neural cell bodies is a slow process. The nature of this process opens up the possibility of therapies. For example, some scientists believe that nerve terminals can be stimulated and regenerated via chemical injections. The new growth of nerves can lead to the re-establishment of synaptic connections necessary for hearing. Since our understanding of nerve damage and hearing loss is still in its earliest stages, much more additional research is necessary. However, with this new information comes new hope for improved public policies and possible therapies.
Source: Science Daily