Hearing loss can either be acute (rapidly occurring, for example with infections or ear wax) or chronic (long-standing). There are three main types of hearing loss: Sensory, Conductive, and Mixed (a combination of the other two).
Sensorineural hearing loss is often called “nerve loss”. This type of hearing loss occurs when the sounds are properly transmitted to the cochlea, but are not processed properly, or the signals that are processed are distorted before they can reach the brain. Several things can cause this type of hearing loss. Some of the most common causes are:
- Changes to the ear due to aging
- Injury to the head that may have damaged the ear
- Infection of the inner ear (virus infections, meningitis, mumps, measles)
- Exposure to loud noise over many years
- Prior exposure to certain medications (some intravenous antibiotics administered for life threatening infections, medications for tuberculosis, or chemotherapy agents given for cancer)
Sensorineural hearing loss is typically permanent, that is, not medically or surgically correctable. It is the most common type of hearing problem in adults. It can be treated, usually very successfully, with hearing aids. Sudden sensorineural hearing losses may actually be reversible with treatment, if caused by a virus.
Conductive hearing loss is caused by any abnormality that blocks sound waves from getting to the inner ear. A blockage in the ear canal can be due to ear wax, swelling from infection, a tumor, or a foreign object in the ear canal (like the end of a Q tip). Abnormalities of the ear drum can also cause a conductive hearing loss. A hole in the ear drum would prevent proper vibration of the drum. A conductive hearing loss may be caused by a problem in the middle ear as well. The middle ear may be blocked due to infection, tumors, or abnormal bone growth. Fluid in the middle ear space (which is common in children) can prevent the ear drum from vibrating properly as well. Even a partial vacuum behind the ear drum, caused by narrowing of the eustachean tube, can lead to a mild conductive hearing loss. These types of hearing loss can typically be treated medically or surgically, often resulting in normal hearing.
Mixed hearing loss, as its name implies, is a combination of the other two types of hearing loss. It is a conductive loss in addition to an underlying sensorineural hearing loss. These types of losses may be treated medically or surgically, often in conjunction with hearing aids. People with this type of loss are very successful users of hearing aids.