Different types of hearing loss in children
There are many different types of hearing loss. If your child has a hearing loss, knowing the type is crucial for choosing effective intervention.
Conductive hearing loss. Plug your ears with your fingers. Are they plugged? Congratulations, you just gave yourself a conductive hearing loss. Fortunately, it's temporary (take your fingers out now--and go wash them before you touch the keyboard again!). A conductive hearing loss occurs due to blockage or structural damage in the ear canal or middle ear. All frequencies are affected equally, so this type of hearing loss can be easily corrected with amplification (hearing aids). In some cases, surgery can repair the damage or remove the blockage, restoring normal hearing. There is no such thing as a good hearing loss, but if you must have one, this is the kind to hope for.
Sensorineural hearing loss results from damage to the inner ear or the auditory nerve, which takes sound impulses from the inner ear to the brain. This type of hearing loss is irreversable and cannot be corrected with surgery. Also, the sensitivity to a given frequency depends on the site of the damage. In other words, you may be able to hear lower frequencies reasonably well, but have trouble with higher frequencies. When this happens, it is difficult, or even impossible, to distinguish among sounds like /s/, /sh/, and /f/. Correction for sensorineural hearing loss usually involves a digital hearing aid, which can be programmed to amplify the specific frequencies the wearer needs.
Mixed hearing loss occurs when there are elements of both conductive and sensorineural factors. Generally, there is damage to the middle ear and the inner ear, as a result of injury, illness, or congenital deformities. In some cases, surgery can correct the conductive issues, but the sensorineural component is irreversible.
In the case of a central auditory processing disorder (CAPD), the outer and inner ear and the auditory nerve are intact, but the brain has difficulty processing the sounds it receives. Areas of particular difficulty for children with CAPD include: listening in the presence of background noise; understanding and remembering directions, lists, and sequences; distinguishing between sounds in words (e.g., hearing bee when someone says key); maintaining attention to listening tasks; and higher-level listening tasks like drawing conclusions, making inferences, or interpreting math "story problems". Only an audiologist can diagnose CAPD, but treatment is usually done by a speech-language pathologist. This is a higher-level processing disorder, so a child with CAPD will be able to pass the kind of hearing screen the public schools provide (the beeps are easier to process than speech). For this reason, plus the fact that a lot of parents and teachers do not really know about CAPD, the approximately 5% of school-aged children who have it are often mis-diagnosed as having attention deficit disorder (ADD). In some very unfortunate cases, they are simply labeled "lazy" or "uncooperative", or accused of "selective hearing".
A bilateral hearing loss affects both ears, but it is possible that the degree or type of hearing loss may not be the same in both ears. For example, one ear may have a moderate conductive loss while the other may have a severe sensorineural loss. This is known as an asymmetrical hearing loss; a symmetrical loss is one in which the degree and type are the same in both ears.
A unilateral hearing loss, as the name suggests, occurs in just one ear; the other ear has normal hearing. A lot of people make the mistake of assuming that a unilateral hearing loss is "no big deal" because the person "can hear just fine" with the unaffected ear. Research has shown, however, that unilateral hearing loss in children is associated with increased risk for speech and language impairments and for difficulty in school. An additional factor with unilateral hearing loss is that it affects a person's ability to localize sound (tell which direction the sound is coming from).
Different types of hearing loss require different intervention approaches.
A person may have two or more different types of hearing loss at the same time; for best results, it is important to address both (or all) of these.
An audiologist is the professional of choice when it comes to diagnosing a hearing loss.
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