Diagnosing Hearing Loss in Babies

By ThinkReliability Staff

All new parents wait to hear that first wail in the delivery room, followed by a quick counting of fingers and toes.  Satisfied with their healthy new baby and exhausted from delivery, few notice the battery of tests newborns face in their first few days of life.  Thanks to these tests, many serious problems can be detected and treated before they become life-threatening.

Many states now mandate hearing screening at birth.  Even minor hearing loss, if not caught early, can seriously impede language and social development.  Nearly 2% of babies fail their initial screening, prompting more through testing.  Approximately 0.2% of children born in the U.S. will be diagnosed with hearing loss.  While most children with hearing loss have conductive (outer or middle ear) or sensorineural (inner ear) hearing loss, there is another type of hearing loss.  With auditory neuropathy (AN) spectrum disorder, sound enters the ear normally; but because of damage to the inner ear or hearing nerve, the brain isn’t able to understand the signal.  The sound is similar to what you might hear underwater or on radio with a lot of static.

Little is known about AN, including what causes it and how to treat it.  Hearing aids seem to help in about half of AN cases, although sometimes children and adults grow out of it.  And some patients thrive with cochlear implants.  Until recently, most weren’t certain how many even suffered from the condition.  A recent study shows that this condition may affect up to 15% of children with born hearing loss.

With all the confusion surrounding AN, few pediatricians and audiologists are aware of this condition or what treatment options are available.  Often the first course of treatment is a hearing aid.  Unfortunately this treatment, which amplifies sound entering the ear canal, can be exactly the wrong treatment for some types of AN.  For those with damage to the hearing nerve, blasting noise into the ear canal simply damages the external, working portions of the ear.  Infants have very sensitive hearing, and just a week of continuous hearing aid use can be enough to cause permanent damage.  Unwitting parents, worried about their children and eager to follow the doctor’s orders, may not realize their children are capable of “hearing”, albeit distortedly, until it’s too late.

A Cause Map can help sort out the factors contributing to this problem.  The top of the Cause Map shows the desired outcome.  Mandatory or recommended screening in infancy results in earlier diagnoses of hearing loss, which limits developmental delays further down the road.  However the bottom portion of the Cause Map shows how current screening practices can often lead to misdiagnosis and the wrong treatment.  By focusing on this area of the Cause Map, solutions can be identified to eliminate the unintended effect.

Two such potential solutions have been identified.  First, changes to the screening process might identify AN early on.  Considering that up to 15% of hearing loss may be caused by AN, this may be a more feasible solution than previously thought.  Second, an awareness campaign may help doctors and audiologists become more aware of AN and how to properly treat it.

With more research and greater awareness, there is hope that those with auditory neuropathy spectrum disorder will not accidently suffer more.  For more information on AN, please visit the National Institute on Deafness and Other Communications Disorders website.