Hearing loss can be categorized into three main types: conductive, sensorineural, or mixed (a combination of the other two). In conductive hearing loss, sound waves are not able to reach the inner ear hearing structures at normal levels. In sensorineural hearing loss, the sound conduction mechanism can be normal, but the inner ear hearing organ or hearing nerve is not functioning properly. These different types of hearing loss can be due to problems with the external, middle and inner ears, as well as the brain.
Hearing loss due to problems with the external ear is usually conductive. The most common cause of hearing loss worldwide is earwax plugging the ear canal. The wax plug interferes with sound waves reaching the eardrum. Similarly, narrowing of the ear canal due to inflammation, bony growths, or from aural atresia will cause a conductive hearing loss. Problems with the eardrum can also interfere with the fidelity of sound transmission. A thickened, scarred, or torn eardrum can’t vibrate normally. This leads to a conductive hearing loss because sound loses energy as it passes through the eardrum. Fluid or blood behind the eardrum from infection, trauma, or allergies can also interfere with the normal vibration of the tympanic membrane and lead to a conductive hearing loss.
Any abnormality of the middle ear bones can also cause conductive hearing loss. If the hearing bones are fixed in position, are lacking a strong connection to one another, or are malformed, they can’t properly transmit vibrations from the eardrum to the inner ear.
Chronic infections and diseases of the middle ear bones can affect their ability to move properly. Tumors and cysts can also grow within the middle ear space and cause erosion of the ossicles.
If a hearing loss is purely conductive and the inner ear and hearing nerve are working well, it’s usually possible to improve hearing by surgically fixing the problem with the external or middle ear.
Hearing loss due to damage to inner ear structures is typically sensorineural. This term refers to a loss occurring either in the cochlea (sensory) or the hearing nerve itself (neural) or both. There are many causes of inner ear hearing loss. The most common is age-related loss, or presbycusis. Other causes include toxins (mercury, some intravenous antibiotics), loud noise exposure, trauma (fracture through the cochlea), viral or bacterial inner ear infections, developmental abnormalities of the inner ear, and tumors.
Each of these causes affects the inner ear in different ways, but many of them lead directly to hair cell loss. While outer and middle ear causes of conductive hearing loss can often be improved with surgery, inner ear hearing loss is usually irreversible. Once hair cells have been damaged or lose their function, there is no way to repair or replace them.The primary treatment for people with some, but not total, sensorineural
hearing loss is a hearing aid. These devices provide a higher volume of sound to the inner ear to make up for the loss of hair cells. If someone becomes deaf in both ears, a cochlear implant can restore some hearing. This device is surgically implanted in the inner ear and replaces
Mixed hearing loss is simply a combination of conductive and sensorineural hearing loss. It’s usually caused by a middle ear problem that also affects the inner ear. For example, chronic ear infections can cause erosion of the ossicles, a conductive loss. But over time, the infection and inflammation can cause damage to the inner ear, leading to a sensorineural hearing loss as well. Mixed loss can also be caused by inner ear malformations.
At House Clinic, all treatment options are offered for the different types of hearing loss, from hearing aids and surgically-implantable devices, to cochlear implants and surgery.