What is a conductive hearing loss (CHL)?
A conductive hearing loss is related to obstruction, disease, malformation, or damage in the middle or outer ear with sound transmission failing to reach the cochlea, or inner ear. Conductive hearing loss can be due to infection, injury or birth defects. Essentially, a conductive hearing loss results from outer and middle ear problems and is usually characterized by a loss of loudness with very little distortion. It is most common in children and often can be medically or surgically corrected. However, a hearing aid may be indicated if the loss cannot be corrected.
What is a sensorineural hearing loss (SNHL)?
A sensorineural hearing loss is caused by disease, malformation, or damage of the inner ear and/or eighth nerve, or hearing nerve. This type of hearing loss is usually characterized by loss of loudness and distortion, making it difficult to understand speech. Hearing aids or cochlear implants are often appropriate forms of intervention.
What is a mixed hearing loss?
A mixed hearing loss occurs when both conductive and sensorineural hearing components are present. Medical or surgical treatment and possibly hearing aids may be indicated with this type of hearing loss.
A child’s mixed hearing loss can be treated with hearing aids, bone anchored hearing implants or cochlear implants.
What is Auditory Neuropathy Spectrum Disorder (ANSD)?
ANSD occurs when the inner ear, or cochlea, functions normally, but an abnormality occurs in the transmission of signals from the cochlea to the brain. In these cases, the Auditory Brainstem Response (ABR) test will be absent or abnormal. Patients may be able to hear, but often experience difficulty understanding spoken words, particularly in noisy environments. Hearing loss can range from mild to profound and can be unilateral or bilateral. Amplification and/or cochlear implantation is often indicated in these patients. While the specific cause remains unknown, researchers believe a number of abnormalities may be responsible.
- Damage to connections between the inner ear and the hearing nerve
- Damage to the cochlear nerve
- Damage to the auditory pathways in the brainstem
Close monitoring of these patients is necessary as wide variation exists between children diagnosed with Auditory Neuropathy Spectrum Disorder.
What is an audiogram?
An audiogram is a chart that is used to plot hearing loss. The numbers across the top represent most of the frequencies, or pitches that humans hear. The numbers to the left are low-pitched sounds, such as a man’s voice. The numbers to the right represent high-pitched sounds, for example, a telephone ringing. The majority of speech sounds occur in the range of 500-4000Hz. The numbers down the side of the chart represent loudness and are defined by decibel level. The loudness increases as you go down the chart. Normal conversational speech occurs at approximately 55dB. A jet engine produces about 120dB of sound.
When is hearing considered normal?
Hearing would be considered normal if results were found between 0 and 15dB. Responses below 20dB are considered as some degree of hearing loss; the further down the audiogram results are noted, the more severe the hearing loss.
Once our Audiology team has completed your child’s testing, we will plot your child’s hearing loss as a line on the Audiogram. Sounds below this line can be heard by your child. Sounds above this line will be difficult to hear or inaudible to your child. Any of our audiologists will be able to discuss appropriate recommendations for treatment if a hearing loss is present.
How to maximize your child’s hearing health and speech and language development:
Have your child’s hearing tested at least annually.
- Be alert for middle ear infections as they can compound the negative effects of your child’s hearing loss.
- Always have your child wear ear plugs during activities with high levels of noise like rock concerts, fireworks, and mowing the lawn.
- Have your child’s vision checked periodically.
- Have your child’s speech, language, and academic progress monitored periodically.
- Talk with your audiologist to determine if a hearing aid or FM system is warranted.
Revised from “Guidelines for Management of School-age Children with Unilateral Hearing Losses” Noel D. Matkin, et al. University of Arizona & Hearing in Children, 4th Edition by Jerry L. Northern and Marion Downs, ©1991. John P. Butler, Editor. Thape 2008, Unilateral and Bilateral Hearing Loss in Children: Past and Current Perspectives. Trends in Amplification, vol. 12; 7 pgs. 7-15.