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Types of Hearing Loss: Conductive, Sensorineural, and Mixed

What Kind of Hearing Loss Do You Have?

As described in our last blog post, the human ear can be divided into three general parts: the outer ear, the middle ear, and the inner ear. Hearing loss can occur in any, or multiple, parts of the pathway from the ear to the brain. Depending on where the hearing loss is occurring, hearing loss can be classified into three different types: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.

Note that in order to determine the type and degree of hearing loss, an audiologist would perform a hearing test and graph the results on an audiogram. In addition, different types of hearing loss require different types of intervention. Make sure to discuss all of your options with a medical provider.

  • Conductive hearing loss occurs when sound cannot be transmitted from the outer ear, to the ear drum, and into the middle ear space (where the smallest bones in the human body, the ossicles, are located). This type of hearing loss can often be corrected medically or surgically. Common causes of a conductive hearing loss may include:
    • Middle ear infection (otitis media)
    • Earwax (cerumen) impaction
    • Fluid or pressure in the middle ear from colds or allergies
    • Poor Eustachian tube function
    • Perforation in the eardrum
    • Head trauma
    • Swimmer’s ear (otitis externa)
  • Sensorineural hearing loss happens when there is damage to the inner ear (the cochlea) or to the nerve pathways from the inner ear to the brain. This is the most common type of permanent hearing loss. And even when speech is loud enough to hear, it may still be unclear or sound muffled. Common causes of a sensorineural hearing loss can include:
    • Aging
    • Exposure to loud noise
    • Genetics (hearing loss that runs in the family)
    • Drugs that are toxic to hearing
  • Mixed hearing loss occurs when a conductive hearing loss happens in combination with a sensorineural hearing loss. In other words, there may be damage in the outer or middle ear as well as damage in the inner ear or auditory nerve. Common causes of a mixed hearing loss can include any combination of the other issues listed above.

 

Hearing Loss and Cognition

The Link Between Hearing Loss and Cognitive Decline

Recently, the Hearing Center at Jacksonville Hearing and Balance Institute partnered with Phonak (a major hearing aid company) to give a presentation to the community regarding the connection between hearing loss and cognitive decline in older adults. Unfortunately, it filled up too quickly for us to accommodate everyone who wanted to attend. Just in case you missed it, here are some of the highlights from the presentation:

The study in question was conducted by Frank Lin, Ph.D. and his colleagues at Johns Hopkins University using information gathered from older adults over a period of decades. The researchers found that those individuals with untreated hearing loss (whether it was mild, moderate, severe, or profound) were significantly more likely to experience cognitive impairments than their normal hearing peers.

But just how are hearing loss and cognitive impairment connected? As Dr. Lin reports, “Your inner ear has to take in a complex sound and convert it into a signal that goes into the brain. When we say that people have hearing loss, it means the inner ear is no longer as good at encoding those signals with accuracy and fidelity. So the brain gets a very garbled message — you can hear what’s being said but you can’t quite make it out. It takes a little more effort to hear what that person said. As a result, the brain has to re-dedicate sources to help with hearing and sound processing. That comes at the loss of something else.” Dr. Lin also notes that, “As we develop hearing loss, we withdraw socially. You’re less likely to go out and you may be less likely to be engaged in conversation.”

While more research needs to be completed regarding the link between hearing loss, social isolation, and cognitive decline, these early results certainly emphasize the importance of hearing heath on one’s overall health. Unfortunately, up to two-thirds of adults with hearing loss remain untreated. Here at JHBI, we hope that by increasing awareness about this topic, we can identify hearing impairments and possible intervention strategies earlier rather than later.

Resources:

Lin, F. R., et al. (2013). Hearing loss and cognitive decline in older adults. JAMA Internal Medicine(4), 173, 293-293. doi:10.1001/jamainternmed.2013.1868