Important Facts About Hearing
Russell H. Griffiths, MD, offers his expertise as an ear reconstruction surgeon with this helpful compilation of facts about hearing. Dr. Griffiths is based in Boise, ID, and seeks to educate parents about the normal function of ears and hearing as well as the hearing problems associated with microtia.
Normal Ear Anatomy
The ear is divided into three sections: the outer, middle, and inner ear. In the diagram below you will see the outer ear includes the external ear (pinna) and the ear canal up to the eardrum (tympanic membrane). The middle ear includes the tympanic membrane and three small bones (ossicles) that conduct the sound from the tympanic membrane to the cochlea called the stapes, malleus, and incus. The middle ear space communicates with the back of the throat above the palate through the eustachian tube. The inner ear contains the cochlea and semicircular canals. The cochlea is curled like a snail shell and contains fluid and small hair cells that transfer sound waves into neural impulses that are then conducted through the auditory nerve to the brain. The semicircular canals are important for balance and help us know when our head is vertical, horizontal, or rotating.
Ear anatomy in Aural Atresia
Aural atresia is a condition where the ear canal does not form properly. It is often associated with microtia (specifically grades 2 to 4). The ossicles are often deformed and in severe cases the cochlea is deformed. Individuals with atresia often have some hearing on the affected side (although severely reduced) from sound waves that travel through the facial and skull bones.
What is the difference between conductive sensorineural hearing loss?
Conductive hearing loss is caused by influences that prevent the sound waves from reaching the cochlea (like aural atresia). Hearing can be significantly improved if the sound can reach the cochlea from either bone conducting hearing devices or through the creation of an ear canal (canalplasty). Sensorineural hearing loss is due to problems associated with the cochlea or nerves.
My child has one good ear and appears to hear fine. Is that good enough?
Unilateral (single sided) hearing loss
Hearing loss in unilateral (one sided) microtia atresia is often misunderstood. Many assume that nothing needs be done for the affected side because the child already has one good ear. This could not be further from the truth. Did you know that up to 80% of children with one sided microtia atresia repeat a grade by sixth grade? Even though they may be of normal intelligence and can respond to others when called upon, the fact that they cannot hear all of the teacher’s words will have an impact on their education level. It will also greatly affect their speech development.
How does this happen? Very simply, all the sounds in the room compete equally for your child's attention. The sound of the other children whispering, the tapping of a pencil, the air pump on the class fish tank, and the janitor’s floor buffer in the hallway all compete with the teacher’s voice. There is a simple experiment that you can do to begin to understand what hearing is like for you child with one sided microtia atresia. The next time you are in a crowded cafeteria, plug one ear with your finger and then try to focus carefully on the conversations around you. You will find it nearly impossible. By having both ears to hear we have the ability to localize sound, and to cognitively ignore one sound spatially to focus on another. Your child with microtia atresia cannot do this.
What can you do to help? Medical research has demonstrated that like a plant without water, the auditory cortex of the brain will begin to atrophy (shrink) if it does not receive input. Bone conducting hearing devices are available that convert sound into vibrations that can bypass the absent ear canal to reach the cochlea which is embedded in the temporal bone. When the device is held against the scalp by a soft headband the vibrations can be heard by the patient. Dr. Griffiths recommends that you try to get a bone conducting hearing device with a soft band for your child as soon as you can (preferably before age 4 months). This hearing device will help stimulate the cochlea on the affected side which will then send nerve impulses to the auditory cortex of the brain. The benefit will be immediate. These devices also can connect via FM signal to a microphone that can be worn on a teacher’s blouse or jacket in a preschool or elementary school classroom and have been shown to significantly improve learning, behavior and speech development.
Second, once your child has a hearing device it is important you are persistent in having him or her wear it as much as possible.
Third, it is very important to maintain the health of your child’s other good ear. Annual audiograms are absolutely essential. Dr. Griffiths recommends you have annual exams by an otolaryngologist in addition to the exams by your normal pediatrician. It is tragic to encounter a patient with one sided microtia atresia who has lost the hearing in their good ear because of recurrent low grade middle ear infections that went unnoticed.
Contact Us to Learn More
Dr. Griffiths offers as much information as he can to every one of his patients and their parents. If you want to learn more about the specific condition that may be affecting your child, contact our practice today.
“My son is experiencing a happiness and a confidence that I have never seen before. You have taken away a big, big hurt...Thank you for making my son happy.” Michael, Father of a Former Patient