Hearing loss can affect an individual's daily life and social relationship. However, there are various causes for hearing loss, making it difficult to make the right diagnosis of the pathogenesis. Now University of Michigan investigators have identified a new cellular mechanism for hidden hearing loss, an auditory neuropathy that contribute to speech discrimination and intelligibility deficits in individuals considered to have normal hearing in traditional tests. The investigators, including Guoqiang Wan and Gabriel Corfas, have reported their findings in the journal Nature Communications.
Some people complain that they have trouble understanding conversation in noisy environments even though they have passed a hearing test. This is the so-called hidden hearing loss. The condition is caused by loss of inner hair cell synapses. This is the only cellular mechanism discovered to date. Now the new study presents a second cause. It reveals that transient loss of cochlear Schwann cells leads to permanent auditory deficits similar to hidden hearing loss. Better understanding the mechanisms underlying hidden hearing loss would be helpful for prevention, diagnosis and treatment.
The cochlea is the auditory portion of the inner ear. Both sensory cells and neurons in the cochlea are essential for normal hearing and auditory communication. Wan and Corfas investigated the effects of Schwann cell ablation in the mature cochlea, as part of their efforts to identify the roles of different types of cochlear glia in hearing.
Schwann cells are supporting cells of the peripheral nervous system. One of their functions is to produce myelin, a lipid substance that forms a sheath around the axons of certain nerve fibers. Using experimental mice, the investigators found that disruption in Schwann cells resulted in hidden hearing loss. They induced myelin loss in the auditory nerve of mice. These mice exhibited permanent hidden hearing loss although the production of myelin was recovered. Collectively, the data suggest that hidden hearing loss may also arise from pathologies of cochlear Schwann cell. In the research, the investigators performed Immunohistochemistry and confocal microscopy, which involves the use of various antibodies.
The study indicates that demyelinating disorders such as Guillain–Barré syndrome may cause hidden hearing loss. In Guillain–Barré syndrome, the immune system attacks the myelin sheath of certain nerves, causing nerve damage. It is reasonable to think that a proportion of Guillain–Barré syndrome patients may develop hidden hearing loss. Guillain–Barré syndrome can be caused by Zika virus. Since the prevalence of Zika infections is on the rise, the prevalence of hidden hearing loss associated with demyelinating disorders may increase.
The study not only presents a second cause of hidden hearing loss, Schwann cell disruption, but also provides clues to why some patients who have recovered from acute demyelinating diseases complain hearing problems. By the way, Cusabio offers Myelin protein P0, Myelin basic protein, anti-human myelin oligodendrocyte glycoprotein polyclonal Antibody, and many other bioproducts such as Recombinant HTR2A.
Hearing loss is ranked the third common health problem in America. It decreases the life quality of affected people. There are already devices such as audiometer and methods such as Weber test and Rinne test to evaluate one's hearing function. But one chief complaint of people with hearing loss is that although they have passed a traditional hearing test they still have trouble hearing out people at a noisy bar or a restaurant. It is critical to create new hearing tests that can identify hidden hearing loss. The new study is a step toward creating such tests.
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