Types & Causes of Hearing Loss
It is important to note that not all hearing loss is the same. There are different types of hearing loss, depending on which part of the hearing pathway is affected. Hearing loss is categorized into four main types: conductive, sensorineural, mixed, and central hearing loss.
Conductive Hearing Loss
In conductive hearing loss, sound waves at normal levels are not able to reach the inner ear. Conductive hearing loss is caused by problems with the outer or middle ear.
Common causes of conductive hearing loss:
- Excessive earwax
- Narrowing of the ear canal due to inflammation or bony growths
- Torn or damaged ear drum
- Fluid or blood behind the ear drum
- Abnormalities of the middle ear bones
- Outer ear deformities
If a hearing loss is purely conductive, it is often possible to improve hearing with medical or surgical treatment. In some cases conductive hearing losses are permanent, but in these cases, individuals can often benefit from hearing aids.
Sensorineural Hearing Loss
Sensorineural hearing loss is the most common, accounting for 90% of all hearing loss. In sensorineural hearing loss, sound waves reach the inner ear, but the inner ear hair cells or hearing nerve are not working properly.
Common causes of sensorineural hearing loss:
- Aging (presbycusis)
- Noise exposure
- Certain drugs
- Inner ear infections
- Developmental abnormalities
Unlike conductive hearing loss, sensorineural hearing loss is usually permanent and cannot be treated medically or surgically. Once hair cells have been damaged, there is no way to replace or repair them. However, many people with sensorineural hearing loss can benefit from hearing aids.
Sensorineural hearing loss accounts for 90% of all hearing loss
Mixed Hearing Loss
Mixed hearing loss is a combination of conductive and sensorineural hearing loss. In mixed hearing loss, sound waves are less efficiently transferred to the inner ear, and if they do reach the inner ear, the inner ear hair cells or hearing nerve are not working properly.
Common causes of mixed hearing loss:
- Any of the causes of sensorineural and conductive hearing losses mentioned above.
Central Hearing Loss
In central hearing loss, sound waves reach the auditory nerve, but the auditory nerve may have problems sending electrical signals, or the brain may not interpret the signals properly. People with central hearing loss are often able to detect sound but may not be able to interpret or understand it.
Common causes of central hearing loss are:
- Head injury
Central hearing loss can be diagnosed using specialized tests that assess a person’s ability to interpret complex auditory information.
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