Types of hearing loss
When any part of the hearing path is damaged, sound information cannot be properly carried to the brain, resulting in some degree of hearing loss. There are three main types of hearing loss: conductive, sensorineural and mixed.
Conductive hearing loss
- Outer ear
- Middle ear
Conductive hearing loss is caused by a blockage of sound transmission through the outer ear or middle ear. This might be due to conditions such as chronic otitis media, otosclerosis (calcification which reduces mobility of the stapes) or a perforated eardum.
Conductive hearing loss can be treated in many ways, including using bone anchored hearing systems like Oticon Medical’s Ponto to bypass the middle ear and transmit sounds via vibration to the cochlea.
Sensorineural hearing loss
Sensorineural hearing loss is caused by problems with the inner ear or nerve pathways. Although sound transmission through the outer and middle ear to the inner ear is normal, this information cannot be coded into electrical signals the brain can use.
- Auditory nerve
- Inner ear
Depending on the location of the dysfunction, the terms cochlear or retrocochlear are used to further define the hearing loss.
Cochlear sensorineural hearing loss is when some of the sensory cells of the inner ear (hair cells) don't function properly. This means the cochlea can no longer transform the sound information it receives from the middle ear into nerve impulses transmitted by the auditory nerve to the brain.These cases can benefit from an Oticon Medical Cochlear Implant System. In some cases, hearing loss only occurs in the high frequency region, resulting in damage to the hair cells located at the base of the cochlea. In this case, combined electro-acoustic stimulation has proven to be effective.
Retrocochlear sensorineural hearing loss is when the auditory nerve itself is affected. The information is processed correctly by the inner ear, but the auditory nerve is incapable of transmitting the nerve impulses to the brain. In these more rare cases Oticon Medical's ABI Brainstem system is typically recommended.
There can be various causes for sensorineural hearing loss, such as presbycusis (aging of the inner ear), congenital causes, prolonged noise exposure,or certain illnesses (such as meningitis).
Sensorineural hearing loss can be progressive and is generally permanent. A traditional hearing aid is often used to overcome mild to severe sensorineural hearing loss. If the hearing loss is severe and the person is unable to communicate effectively with a hearing aid, a cochlear implant
can be recommended.
If the cochlea is severely ossified, or if the auditory nerve is no longer functioning, a cochlear implant will not help. In some cases, alternatives to a cochlear implant can help, such as an auditory brainstem implant.
Mixed hearing loss
- Auditory ossicles
Mixed hearing loss is a combination of conductive hearing loss and sensorineural hearing loss. As an example, a chronic infection could cause mixed hearing loss if it damages the eardrum and the ossicles and prevents the cochlea from functioning properly.
Individuals who suffer from this type of hearing loss may also benefit from the use of a bone anchored hearing system like Oticon Medical’s Ponto.