New study shows sound deprivation can lead to permanent hearing loss
If you have a feeling of fullness in one ear, or voices sound muffled, the results of a new research study show that it could be a problem with long term consequences if left untreated. But the good news is that a simple visit to a hearing care professional could not only prevent further problems down the road, but might just save your hearing.
The new study, done at Eaton-Peabody Laboratories at the Massachusetts Eye and Ear Infirmary, investigated whether the auditory deprivation that occurs from adult onset chronic conductive hearing loss could have long term, lasting effects. Conductive hearing loss is hearing loss that occurs when sound transmissions from the ear canal to the inner ear are impaired or blocked. Causes of conductive hearing loss can include something as simple as an earwax blockage, or could be a result of an ear infection (otitis media) or otosclerosis (an abnormal bone growth of the middle ear).
First, though, we’ll explain how hearing works, and why it is important that all three sections of the ear work together without impediment: First, the sound waves travel through the ear canal (the outer ear). Those sound waves then reach the eardrum and bones of the middle ear. The middle ear is where most conductive hearing loss originates. If sound is blocked at this point, then those sounds are unable to be sent on to the inner ear, where they would be converted into electrical signals for transmission to the brain by the auditory nerve.
The new research was conducted on mice with unilateral conductive hearing loss, meaning they only experienced sound deprivation in one ear. Results of the study, recently published in PLOS ONE, showed that a period of auditory deprivation caused irreversible damage to the inner ear; the damage manifested itself in a significant loss of the vital connections between the sensory cells and the brain.
“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,” said Dr. Stephane F. Maison, Ph.D., lead researcher on the study and assistant professor of otolaryngology at Harvard Medical School. “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.”
Researchers also noted that the mice in the study experienced damage to hearing mechanisms which mimicked that of age-related or noise-induced hearing loss.
So what does all of this mean for humans? It means that there is a possibility that the auditory deprivation caused by chronic conductive hearing loss, whether from ear infections, blockages or other medical issues, can lead to permanent hearing loss if left untreated. The findings may be especially significant for children, since 80 percent of kids will have at least one ear infection before age 3 and many children suffer from chronic ear infections. Ear infections are the most common cause for doctor visits and prescriptions for children, and those chronic ear infections can lead to “communication deficits” that persist long after the ear infections subside.
For adults, problems are more likely to occur when they experience problems in just one ear, so just opt to use their “good ear” instead of seeking treatment. And for children, physicians often advocate for waiting as long as two to three months before checking to see whether effusion (fluid that builds up behind the eardrum, and may or may not be the result of an infection) has cleared. Those months of waiting are often accompanied by diminished hearing, which can lead to communication delays at a crucial time in speech and language development. Researchers are hopeful that for both children and adults, the results of the study will change the approach to conditions of the middle ear from a “wait and see” stance to one of more immediacy.
"Our findings suggest that audiologists and physicians should advocate for early intervention and treat these middle ear conditions," said Maison.
If you or your child are experiencing trouble hearing, ear pain, muffled hearing or a feeling of fullness, don’t put off seeking treatment in the hopes that the problem will resolve itself, or because you can simply “use the other ear." It is important to make an appointment with your physician or hearing healthcare professional as soon as possible; that one phone call might make all of the difference to your hearing down the road.