Sound deprivation in adult mice was found to cause irreversible hearing loss. The findings were uncovered by researchers at Massachusetts Eye and Ear Infirmary. The findings suggest that chronic conductive hearing loss – which can occur with reoccurring ear infections – can lead to permanent hearing loss if left untreated.
To hear, sound waves move in through the ear canal and reach the eardrum and the tiny bones in the middle ear. This is then converted into electrical signals in the inner ear that travel to the brain by the auditory nerve. When the transmission of sound from the ear canal to the inner ear is impaired it causes conductive hearing loss. This can contribute to a loss of hearing soft sounds.
The research team, led by Stephane F. Maison, Ph.D., examined changes in the inner ear of mice with chronic conductive hearing loss.
Dr. Maison said, “After a year of sound deprivation, we observed dramatic changes in the inner ear – notably, a significant loss of the synaptic connections through which the sensory cells send their electrical signals to the brain. Although there have been many studies of acoustic deprivation on the auditory system, few have looked at adult-onset deprivation, and none, to our knowledge, has documented changes in the inner ear.”
Common causes of conductive hearing loss are earwax blockages, ear infections and otosclerosis.
“Although these conditions are routinely treated in industrial societies, a number of patients choose not to receive treatment, particularly when their medical condition affects only one ear. For instance, patients with unilateral atresia, a condition in which the ear canal is closed or absent, see limited benefits of undergoing surgery when they can simply use their good ear,” Dr. Maison explained.
Nearly 80 percent of children will experience otitis media before the age of three. Ear infections are also quite common among children. Bouts in communication deficits can carry on for years, even after the infection in the middle ear has been resolved.
The new findings suggest that sound deprivation can damage the ear the same way as age-related and noise-induced hearing loss can. The mechanisms of what cause hearing loss due to sound deprivation are still unknown, but researchers suggest the effects need to be managed within clinics when treating conductive hearing loss.
Dr. Maison concluded, “Our findings suggest that audiologists and physicians should advocate for early intervention and treat these middle ear conditions.”
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