The part of the ear affected, the cause, and how quickly it is identified or treated will determine if a loss is temporary or permanent.
Conductive Hearing Loss
This is any physical abnormality, blockage, or damage to the outer or middle ear which prevents sound from reaching the inner ear. It results in a reduction of sound loudness. When sound is made loud enough, children with conductive hearing loss have minimal difficulty understanding speech. Possible Causes:
- excessive amounts of wax blocking the ear canal
- blockage of the eustachian tube (caused by colds or infection) causing fluid in the middle ear
- puncturing of the eardrum, resulting from trauma or infection
- disconnection or fixation of the middle ear bones
- foreign body in the ear canal
- deformity of the outer or middle ear
With the exception of physical deformity, most conductive hearing losses can be treated medically or surgically. Conductive hearing losses can re-occur so monitoring is necessary. (Recurring middle ear fluid is particularly common in children.) Also, if left untreated, conductive hearing loss can become permanent. Treatment then becomes hearing aid amplification with assistive devices as necessary.
Sensorineural Hearing Loss
This is caused by damage to the cochlea creating an inability to change mechanical energy from the middle ear to electrical impulses to the auditory nerve. It results in a reduction of sound quality. Not only is sound not loud enough to detect, when it is made loud enough there is significant distortion which will effect a child’s ability to understand speech. Possible Causes:
- associated with other medical conditions
- medication toxic to the ear
- breathing problems at birth
- noise exposure
Sensorineural hearing losses cannot be corrected medically or surgically. When an indiviual is diagnosed with sensorineural hearing loss it is essential that they be fitted with hearing aid amplification as quickly as possible. Further, they will need to be seen by a Speech – Language Pathologist to assess language and communication needs. Assistive listening devices may also be necessary.
Auditory Nerve Impairment
This is caused by disease or damage to the central auditory nervous system preventing the interpretation of speech. Depending on where the disorder occurs, there can be a slight inability to hear in background noise or a total inability to understand speech. Possible Causes:
- delayed or disordered auditory nerve development
- lesions on the auditory nerve
- neurodegenerative disorders
Mixed Hearing Loss:
Conductive, sensorineural and auditory nerve impairment can occur simultaneously which can cause delays in appropriate diagnosis and long term treatment.