Hearing loss – types and effects

There are three types of hearing loss. Below is a brief description of them.

Sensori-neural
Sensori-neural hearing losses are caused by damage to the hair cells of the inner ear, auditory nerve or brain. There are several causes of sensori-neural hearing losses such as noise exposure, ageing, meningitis, genetic factors, certain drugs, certain pre-natal conditions, some viruses, etc. Most, but not all, sensori-neural hearing losses are permanent and do not get better. A majority of people with sensori-neural hearing losses can be helped with amplification. Often people with sensori-neural hearing loss will experience tinnitus, or ringing in the ear.

Conductive
Conductive hearing losses are caused by some physical blockage or mechanical problem, which interferes with sound transmission through the outer or middle ear. Causes of conductive hearing loss include wax blockage, perforated ear drum, the various forms of otitis media, otosclerosis, a break in one of the middle ear ossicles, etc. Most, but not all, conductive hearing losses can be medically and/or surgically treated, resulting in improved hearing, frequently to near normal levels. Some people with conductive hearing losses use amplification.

Mixed
A mixed hearing loss has both conductive and sensori-neural components to the loss. As in pure conductive hearing losses, medical and/or surgical intervention with the conductive component can often improve the hearing.

The effect of hearing loss

To understand the effects of hearing loss it is important to understand the need for good hearing. Good hearing is essential for the development of normal language and communication. Even a mild, fluctuating conductive hearing loss, which can be associated with otitis media, can have a negative effect on language and learning in many children.
If a child has a hearing loss it will cause problems in the development of various skills. The amount of problems that happen will depend on two main aspects of the hearing loss:

• The age of onset – the earlier in the child’s life, the greater these skills are impacted.
• The degree of hearing loss – the greater the hearing loss, the greater these skills are affected.

These are some of the effects of different degrees of hearing loss on learning and classroom performance:

Slight (16 – 25 dB)
Understand conversation at 3 m
Speech/language development may be affected because of hearing loss
Should understand most classroom discussion
A few children may require some degree of amplification

Mild (26 – 40 dB)
Understand conversation at 1 – 1.5 m
May have delayed speech/language development
Will miss up to 50% classroom discussion
Will need amplification, hearing aids or FM system
May need special education attention

Moderate (41 – 55 dB)
Understand conversation at 0.5m
Will have difficulty at school
Likely will have speech/language delay
Will require hearing aids and/or FM systems
Will need special education assistance and probably special training for listening
Uses vision for additional cues to understand spoken messages

Moderately Severe (56 – 70 dB)
May understand speech at ~25 cm
Will hear moderately loud environmental sounds
Will have delayed speech/language
Requires use of hearing aids and FM systems
Will need special education assistance and special training for listening

Severe (71 – 90 dB)
May understand some speech at <15 cm
Hears loud environmental sounds
Will have delayed speech / language
Requires use of hearing aids and FM systems
Requires auditory training
Uses vision for additional cues to understand spoken messages
Speech / language will not develop spontaneously if loss present before 1 year old
May be a candidate for cochlear implantation

Profound (> 91 dB)
May only be aware of very loud sounds
Speech and language will be defective
Visual and gestural cues essential for learning
Needs full time special education assistance
Requires use of a hearing aids and FM systems
May be a candidate for a cochlear implant