terms
• Conductive
• Sensorineural
• Auditory
Neuropathy/Auditory
Dys-synchrony
• Acquired / Genetic
• Risk Factors
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TOPIC CARD 2
Types and
Causes of
Hearing Loss
2
Questions
Q
• How common is hearing loss?
• Is my child’s hearing loss permanent?
• What caused my child’s hearing loss?
• What are “risk factors”?
• What are the medical and audiological
treatment / management recommendations
for the various types of hearing loss?
• How can my child have a hearing loss
when the birth hearing screening was passed?
• How common is hearing loss?
Hearing loss in young children is more common than you may think – approximately three out of every
1,000 babies have some type of hearing loss. In fact, hearing loss is more common than all of the other
disorders (e.g. PKU, sickle cell anemia) for which newborns are tested in the hospital.
• Is my child’s hearing loss permanent?
There are several different types of hearing loss.
Conductive hearing loss is usually “medically treatable.” Depending upon the cause of the conductive
loss, treatment outcomes vary. Conductive hearing loss, caused by fluid behind the tympanic membrane
(eardrum), may change with the amount and thickness of the fluid; treatment is usually very effective in
restoring normal hearing levels. Some conductive hearing loss, caused by malformation of the ear canal
and/or the bones of the middle ear, may be permanent even after treatment.
Sensorineural hearing loss is a permanent hearing loss due to non-functional inner ear/cochlear sensory
cells (hair cells). Sometimes, the cause of a sensory hearing loss can be traced to a specific factor, but the
cause is often unknown.
Mixed hearing loss is a combination of the conductive and sensorineural hearing losses. While the
conductive component may be managed with medical treatment, the sensorineural component is
permanent.
Auditory Neuropathy/Auditory Dys-synchrony Currently, these are terms that describe a newly
identified hearing condition that involves inefficient processing of sound somewhere between the inner hair
cells in the cochlea and the brain. Based on what is currently known through research, this general
disorder is thought to be caused by a number of different pathologies resulting in some varieties that are
permanent and some varieties that are temporary.
• What caused my child’s hearing loss?
An acquired hearing loss is a non-hereditary loss that results from conditions or events that occur during
pregnancy, during birth or after birth. These causes may be related to infections of the mother during
pregnancy, illnesses of the child after birth, or complications that occur during birth including lack of
oxygen. However, nearly 50% of infants with hearing loss have no known risk factors. Many of these
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hearing losses are genetic. If there is no clear cause for the hearing loss, your audiologist may recommend
genetic counseling to help answer questions about the potential for future children in your family to have
hearing loss. Genetic counseling can also help in the identification of other possible disorders associated
with hearing loss. Recent advances in genetics have shown that genetic hearing loss is more common
than previously thought.
• What are “risk factors”?
A “risk factor” is a medical condition or event that is known to be associated with hearing loss. The
presence of a risk factor does not guarantee that there will be a hearing loss, only that children with one
or more of these specific conditions have a higher risk of permanent hearing loss. Hearing loss risk factors
include: family history of childhood hearing loss, infection during pregnancy including cytomegalovirus
(CMV) and toxoplasmosis, anomalies of the head and neck (physical difference or abnormality of the head
and neck such as a malformed ear), low birth weight, hyperbilirubinemia (jaundice), bacterial meningitis,
ototoxic medications, mechanical ventilation, and low Apgar scores. There are more detailed criteria for
some of these risk factors. Please discuss concerns or questions with your doctor.
• What are the medical and audiological treatment/management recommendations
for the various types of hearing loss?
Conductive hearing loss caused by middle ear fluid may be corrected with medical treatment such as
antibiotics or minor surgery. Conductive loss caused by malformation of the ear canal and middle ear may
require more extensive surgery; this surgery may be delayed several years for medical reasons. Children
with conductive loss often wear a bone conduction hearing aid during the interim. Bone conduction
hearing aids are normally very effective when the loss is purely conductive.
Sensorineural hearing losses are managed using hearing aids and/or cochlear implants. The effectiveness
depends upon the degree of hearing loss, the age at which hearing loss is identified and early intervention
begins, the consistency with which the hearing aids or implants are worn, and the consistency and
effectiveness of early intervention. In general, the earlier the identification and intervention and the more
consistently the hearing aids or implants are worn, the better the outcome.
Mixed hearing loss is managed with combinations of the treatment/management strategies described
above depending upon the child’s individual hearing loss characteristics.
Auditory Neuropathy /Auditory Dys-synchrony is currently managed with hearing aids, assistive
listening devices and/or cochlear implants, depending upon the symptoms of the disorder. A standard of
care has not yet developed and research into the underlying causes of this condition continues. At this time
ongoing hearing evaluation and evaluation of the child’s language helps to guide decisions about
management including decisions about communication methods.
• How can my child have a hearing loss when the birth hearing screen was passed?
If your child passed a hearing screening at birth, but now has a hearing loss, it is likely that one of the
following is true: 1) a medical event occurred which caused the hearing loss to develop (meningitis, other
viral infections like CMV, ear infections causing middle ear fluid, etc.). 2) a medication given to your child
as a treatment for a potentially life-threatening condition caused the hearing loss. 3) your child has a
genetic disorder in which hearing loss develops and progresses some time after birth. If your child had any
of the risk factors listed above, his or her hearing should be tested regularly even if the screening at birth
did not indicate a hearing loss.