Meaning of Hearing Loss
- The ear consists of three parts:
- The external, visible part with the ear and ear canal.
- The middle part (middle ear) with ear drum and ossicles (small bones used for hearing).
- The inner part (inner ear) with the cochlea and hair cells
Patients with Microtia and atresia usually have an intact inner ear, as this part of the ear doesn’t develop from the gills. Therefore, the type of hearing impairment is mainly a pure conductive hearing loss and in such cases amounts to a loss of around 60 to 70 dB or around 75%. The affected ear is unable to detect many everyday sounds. When both ears are affected, this has a negative impact on the speech and general development of children with these conditions. They need a headband hearing aid in the first few weeks after birth.
In recent years, the assessment of the effects of single-sided deafness is now quite different than it was previously. While one ear is enough for normal speech and development, children with single-sided deafness reach the limits of their hearing ability in difficult listening situations. Examples of difficult listening situations include when different conversations are taking place in the same room, listening when music or noise is present. Children are faced with these situations when they first go to school and they can only be partly compensated. The directional hearing of children with single-sided deafness is also very limited. It is thought that the school performance of at least a third of all children with single-sided hearing loss suffers. That is why early treatment for single-sided malformations as well is recommended.
There are a few types of hearing loss where a bone conduction sound processor may be able to help an individual hear again. Only an audiologist and ENT can determine if an adult is a candidate for a bone conduction sound processor depending on the type of hearing loss and how severe it is. These types of hearing losses are:
Bone Conductive Hearing Loss
A hearing loss that can occur when sound traveling from the outer ear can no longer make it to the inner ear. This can happen if there is no means of a pathway to help transfer the sound from the outer ear (environment) to the inner ear (cochlea and auditory nerve). A common example of a conductive hearing loss is atresia (absence of the ear canal where sound has no pathway to travel to the inner ear). Sound must be able to make it in to the inner ear though the ear canal along with making it through the tympanic membrane, then through the middle ear bones and into the inner ear and then to the auditory nerve for the brain to interpret the sound waves as communication. Other examples that may cause a conductive hearing loss are: fluid in the ear, ear wax (cerumen) build up, ear infection, a tumorous growth (cholesteatoma), or trauma to the ear from loud music or from an traumatic accident.
Sensorineural Hearing Loss (SNHL)
A hearing loss that can occur gradually over a lifetime or almost overnight and can be mild, moderate or severe, including causing permanent hearing damage resulting in total deafness. Sensorineural hearing loss is mainly caused by the tiny hair cells within the Cochlea that are no longer able to transfer sound information to the auditory nerve allowing the brain to interpret sound as communication. Although sound may still be heard, the quality of the sound is perceived to be so poor that speech cannot be understood. These hair cells may have been damaged at birth or damaged during an individual’s lifetime (such as exposure to very loud noises in one’s work environment). Some examples of symptoms of sensorineural hearing loss are: dizziness, ear infections, sudden loss of hearing or gradual degradation of hearing. Meningitis, Measles or the Mumps may cause hearing loss. Sensorineural hearing loss may also be genetic due to certain syndromes as well.
Mixed Hearing Loss
A hearing loss that is both conductive and sensorineural. Mixed hearing loss can be both partial or complete hearing loss. Mixed hearing loss can be the result of sound simply not being able to make it from the external ear to the middle ear and also the result of sound signals not being able to be transmitted correctly due to the hair cells no longer functioning properly within the cochlea preventing the brain from being able to interpret the sound waves into communication signals. Mixed hearing loss can be the result of fluid in the ear (some form of blockage from the ear canal to the cochlea), traumatic injury (exposure to loud noises over time causing hearing degradation), genetic (born with poor hair cells), or something that happens in time. Mixed hearing loss symptoms may include the same involved with both sensorineural and conductive hearing losses.
Summary of Soundbridge Surgery