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Single Sided Hearing Loss in Children

The Importance of Two Ears

Many professionals will tell parents not to worry about single sided AM because ‘your child hears fine with one ear.’ That is partly true, but unfortunately only in quiet. It is not true in normal everyday situations. Traditionally, physicians and audiologists were taught that if one ear is normal then auditory, speech, and language function and development will be normal but with advances in human development research, we now know this long-held belief is wrong.

Untreated single sided hearing loss in children produces several functional and developmental problems. In summarizing the research articles listed at the end of this section, it is fair to say “the more difficult the listening situation the more dysfunctional single sided hearing becomes”. For example, a child with unilateral hearing impairment will function relatively normally at home in a quiet environment with a single person interaction with known speakers. That same child may have extreme difficulty in a noisy classroom. Even if teachers, parents, and professionals think the child is doing “just fine” with hearing only on one side, it is well documented that untreated single sided hearing loss has a significant potential impact on numerous levels.

Everyone has had the experience of being in a restaurant that becomes progressively noisier during the evening. The ear’s job in that situation is to take all the sounds to the brain including the kitchen noise, chairs moving, other table conversation, glasses touching in a toast, etc. The brain’s job is to extract the words from the person across the table you are trying to listen to. Through very complex neural processing, the brain can extract the words we want to focus on if it has two ears to work with. People with a single hearing ear will understand over 95% of spoken communication in quiet. In people with two normal hearing ears, background noise will cause a slight drop in understanding to the 85-90% range. With single sided hearing loss, understanding drops all the way down to the 50-60% level with background noise present.

Two ears are needed for the optimum functioning and development of a child. Our goal is always to allow each child and patient reach his or her best performance status. You will hear us say “it is not a question of IF but HOW we get hearing to each ear.”

Why repair single sided hearing loss localize sound graphic Why repair single sided hearing loss in children localize sound graphic

Here are summaries of the different functions two ears allow:

  • Sound Localization:

When a sound comes at us from any angle the brain measures the difference in time it takes for the sound to reach each ear. For example, a sound coming from the right will register in the right ear before it does in the left. This intra-aural time difference is very small, but when two ears hear a sound at slightly different times, the source of the sound can be “localized” and the listener can turn to it if desired. Just like the loss of vision in one eye eliminates depth perception, the loss of hearing in one ear eliminates the hearing equivalent which is sound localization.   On a sports field or in a parking, the deficit of single sided AM becomes evident when a child will hear their name being called but have to scan the environment to locate the source.   We believe this is one of the reasons children with hearing loss have almost twice the rate of injury than those with normal hearing in both ears.

  • Binaural Loudness Summation

When two ears hear a sound, it registers more loudly with the brain than if the same decibel level sound was only heard with one ear. This makes sense when you know that nerve cells in the brain which register sound receive input via nerve connections called “axons” present in both ears. With a sound, the brain hearing nerve cell will have a stronger stimulation with the same sounds when two ears hear it instead of one. Intelligibility in low volume situations improves significantly with two ears compared to one.

  • Hearing in Noise

Every day we select out the speech we want to listen to from a sea of noise. To go back to our analogy above, all of us have had trouble in very noisy situations (like a restaurant or party) hearing what another was speaking to us. The brain, not the ear, is responsible for our ability to selectively listen in noise.  Without two ears, a child will have difficulty hearing in even small amounts of background noise. Every brain is different in its ability to perform this task and testing can be done to quantify the function. On some occasions, the brain has trouble with this task even when two normally hearing ears are present – called Auditory Neuropathy. Children with one hearing ear have functional Auditory Neuropathy.

  • Language Acquisition

It has been conclusively shown that children who have hearing loss in one ear will develop less language and language specific skills, as well as have a lower verbal IQ.  Lower rates of reading capability, graduation from high school and academic performance are also well documented in the research.

  • Cognitive Load

Understanding speech in noisy environments while conducting tasks is difficult even for people with normal levels of hearing. The louder the background noise, the longer it takes the individual to complete the task and the more speech they miss. This concept is called “cognitive load” and can represent a subtle but constant problem for school-aged children attempting to understand what a teacher is saying while taking notes in a noisy classroom.

  • Head Shadow Effect

A person with normal hearing and brain function can preferentially listen with one ear instead of the other. Imagine you are walking down a sidewalk with traffic to one side and a friend talking to you from the other. Your brain will preferentially listen to your friend and “turn down” the ear toward traffic to improve your understanding. Now imagine a teacher walking around a classroom (they ALL are noisy to some extent) and imagine what happens when the teacher walks to the side with hearing loss or turns to write on the blackboard. With that image, you can understand how two ears are preferable to a single ear in the classroom and other life situations.

So what impact should this have on how I treat my child?

For this reason and the reasons listed above, it is our medical objective to return hearing to two ears if at all possible and as early as possible. As stated above, in the past, physicians have been historically taught that one ear is “good enough” and many do not recommend treatment of single sided deafness. These physicians, who are poorly informed about the current research, do not perceive a problem in delaying treatment of single sided hearing loss during the very critical period of development of the auditory system during the first few years of life. Unfortunately, this delay can create permanent and irreparable harm to the child whose hearing loss goes untreated.

Situations must be assessed individually by a professional well experienced with the unique challenges of atresia and the treatment options available. These options may change over time as well.  Surgery to perform atresia repair at the appropriate age may be the right choice if a CT indicates a high chance for success. For others, surgery for atresia repair is not the best option and other devices may be the appropriate long-term solution.  Again, the question isn’t IF but HOW to get hearing to each ear.

In the links below includes one of the earliest studies on untreated hearing impairment, as well as more recent research on the topic, and the conclusions continue to be quite definitive.

Comparison of Unilaterally Hearing-Impaired Children and Normal-Hearing Children and Normal-Hearing Children on a Battery of Standardized Language Tests

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Pediatrics Official Journal of the American Academy of Pediatrics
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Many of the studies that have helped lay ground in the current recommendations for intervention and have helped guide the way we practice are also listed below if one wishes to investigate further.

Paper: Effects of Aural Atresia on Speech Development and Learning Retrospective Analysis From a Multidisciplinary Craniofacial Clinic.

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References:

Bess FH, Tharpe AM. Case history data on unilaterally hearing-impaired children. Ear Hear 1986;7(1):14-19.

Culberson JL, Gilbert LE. Children with unilateral sensorineural hearing loss. Ear Hear 1986;7(1):38-42.

Oyler RF, Oyler AL, Matkin ND. Unilateral hearing loss: Demographics and educational impact. Lang Sp Hear Serv Schools 1988;19:201-210.

Ovo R, Martini A, Agnoletto M, et al.. Auditory and academic performance of children with unilateral hearing loss. Scand Audiol Suppl. 1988;30:71-74.

Jensen JH, Borre S, Johansen PA. Unilateral sensorineural hearing loss in children: Cognitive abilities with respect to right/left differences. Brit J Audiol 1989;23:215-220.

Bess FH, Tharpe AM, Gibler AM. Auditory performance of children with unilateral hearing loss. Ear Hear 1986;7:20-26.

Keller WD, Bundy RS. Effects of unilateral hearing loss upon educational achievement. Child: Care Health Dev 1980;6:93-100.

Stein D. Psychosocial characteristics of school-age children with unilateral hearing losses. J Acad Rehabil Audiol 1983; 16:12-22.

Dancer J, Burl NT, Waters S. Effects of unilateral hearing loss on teacher responses to the SIFTER: Screening Instrument for Targeting Educational Risk. Am Ann Deaf 1995;140:291-294.

McKay S. To aid or not to aid: Children with unilateral hearing loss. Health Hear 2002. Retrieved May 11, 2007 from www.healthyhearing.com/library/article_content
.asp?article_id=163.

Reeve K, Davis C, Hind S. Mild and unilateral hearing impairments: What the clinicians think. Poster presentation at A Sound Foundation Through Early Amplification Conference, October 2001. Chicago.

Brookhauser PE, Worthington DW, Kelly WJ. Unilateral hearing loss in children. Laryngoscope 1991;101(12, pt 1):1264-1272.

English K, Church G: Unilateral hearing loss in children. An update for the 1990s. Lang Sp Hear Serv Schools 1999;30:26-31.

Hartvig Jensen J, Borg S, Johansen PA: Unilateral sensorineural loss in children. Cognitive abilities with respect to right/left ear differences. Brit J Audiol 1989;23(3):215-220

Spitzer JB, Ghossaini SN, Wazen JJ. Evolving applications in the use of bone-anchored hearing aids. AJA 2002;11(2):96-103.

Wazen JJ, Spitzer J, Ghossaini SN, et al.. Results of the bone-anchored hearing aid in unilateral hearing loss. Loaryngoscope2001;111(6):995-958.

Reeve K. Amplification and family factors for children with mild and unilateral hearing impairment. In National Workshop on Mild and Unilateral Hearing Loss: Workshop Proceedings. Breckenridege, CO: Centers for Disease Control and Prevention, 2005:20-21.

Jerger J, Silman S, Lew HL, Chmiel R. Case studies in binaural interference: Converging evidence from behavioral and electrophysiologic measures. JAAA 1993;4:122-131.

Davis A, Reeve K, Hind S, Bamford J. Children with mild and unilateral impairment. In Seewald RC, Gravel JS, eds., A sound foundation through early amplification 2001: Proceedings of the Second International Conference, Great Britain: St. Edmundsbury Press, 2002: 179-186.

Peters BR, Litovsky R, Parkinson A, Lake J. Importance of age and post implantation experience on speech perception measures in children with sequential bilateral cochlear implants. Otology & Neurotology 2007;28:649-657.

Sharma A, Dorman M, Spahr A. A sensitive period for the development of the central auditory system in children with cochlear implants: implications for age of implantation. Ear & Hearing 2002; 532-539.

Sharma A, Dorman M, Kral A. The influence of a sensitive period on central auditory development in children with unilateral and bilateral cochlear implants. Hearing Research 2005; 203:134-143.

Snik FM, Teunissen B, Cremers WRJ. Speech Recognition in patients after successful surgery for unilateral congenital ear anomalies. Laryngoscope 1994;204:1029-1034.

Breier JI, Hisocock M, Jahrsdoerfer JA, Gray L. Ear advantage in dichotic listening after correction for early congenital hearing loss. Neuropsychologia 1998;36(3):209-16.

Mann JR, Zhou Li, McKee M, McDermott S. Children with Hearing Loss and Increased Risk of Injury. Annals of Family Medicine 2007; 5:528-533.

U.S. Census Bureau, 1997. Survey of Income and Program Participation tables.

Kochkin, S. The Impact of Untreated Hearing loss on Household Income, August 2005, Better Hearing Institute, Alexandria, VA, viewable at

http://www.betterhearing.org/PDFs/MarkeTrak7_ImpactUntreatedHLIncome.pdf

 


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