When hearing loss occurs it is because one or more parts of the ear are not performing correctly. There are three different kinds of hearing loss. There is conductive hearing loss, neural hearing loss, and sensory hearing loss. When a person has conductive hearing loss it is usually associated with a problem with the outer or middle ear. Conductive hearing loss is usually temporary. Neural hearing loss is related to nerves. The cochlea is unable to properly connect to the brain. Sensory hearing loss is associated with the cochlea and is usually permanent.
Hearing loss can be causes by many different factors. A person may have been born with parts of the ear not formed properly. Hearing loss can also be associated with head injuries, multiple ear infections, and working in a very loud environment (or listening to music that is too loud).
Sounds are perceived when sound waves pass through the 3 main structures of the ear. Hearing loss occures when one or more structures are affected.
These structures are:
- External ear canal;
- Middle ear, which is separated from the external ear canal through the tympanic membrane (eardrum);
- Inner ear, which contains the cochlea, the main sensory organ of hearing.
Depending on the affected structures of the ear, hearing loss can be of several types:
- impaired sound transmission (transmission deafness): sounds do not reach the inner ear, this situation occurs when the ear wax or growths block the sound transmission, such as in otosclerosis;
- Hearing loss of sensorineural cause (sensorineural deafness): examples of the sensorineural hearing loss include both noise-related hearing loss and age hearing loss.
Another category of hearing loss is due to central causes. In this type of illness, ear structures function normally but there was a cortical damage of the structures that control hearing, blocking the sound understanding. This can occur after a head injury or a stroke. This type of hearing loss is very rare.