The Pediatric Ear, Hearing, and Balance Center at the Massachusetts Eye and Ear Infirmary provides state-of-the-art multidisciplinary care for infants and children who have severe to profound hearing loss and may be candidates for a cochlear implant. We are the only center in Boston that provides both experience and expertise for all three FDA approved cochlear implants made by Advanced Bionics Corporation, Med-El Corporation, and Cochlear Corporation.
Cochlear implant candidates are seen and evaluated by a pediatric otologic surgeon, pediatric audiologist, and a speech therapist. Additionally, children who have congenital hearing loss and whose parents are interested in pursuing full developmental and genetics evaluation are referred to our colleagues at the Massachusetts General Hospital for Children, who can then provide state-of-the-art testing and evaluation of an infant or child who has a congenital hearing loss. This is done to ensure that there are no other conditions associated with a child’s hearing loss, as well as to determine the potential cause of the hearing loss through genetic testing.
Infants and children who are found to be cochlear implant candidates can undergo implant surgery one ear at a time, or simultaneously in both ears, based upon the family’s wishes and the child’s hearing loss status.
What is a cochlear implant?
A cochlear implant is not a hearing aid. It is the most successful example of a bionic device interfacing with the human brain. It replaces the cochlea, a special sensory organ, with an implant that provides electronic sensations to the hearing nerve or auditory nerve found in the inner ear. This is the portion of the device that is surgically placed during a 1-2 hour outpatient surgery. This internally implanted device communicates wirelessly across the skin with an internally placed speech processor which has a battery, microphone, and electronics to convert sound to an electronic signal that is then transmitted via an FM antenna to the internally implanted device. If the child has profound hearing loss at birth, habilitative services as well as continued and close follow up with Audiology are absolutely important to ensure success with the cochlear implant in order to achieve speech and language skills associated with enhanced sound and speech perception with the cochlear implant.
Therefore, the cochlear implant bypasses the non-functioning hair cells of the inner ear to electrically stimulate the auditory nerve. The signal is then sent to the higher processing cells in the brain to provide enhanced sound and speech understanding.
Who is a candidate for cochlear implants?
Patients are evaluated by a pediatric otologic surgeon, a pediatric audiologist, and a speech therapist. Testing and evaluation at the Massachusetts General Hospital for Children is also recommended for those with a history of congenital hearing loss and whose parents are interested in pursuing such options. Children are also seen in Ophthalmology to insure that there are no other associated eye problems with the hearing loss. Children also undergo imaging which might include a temporal bone CAT scan or MRI scan of the skull base and of the brain. These imaging modalities are complimentary. For those found to have a connexin 26 mutation, imaging is not necessary as there is generally normal inner ear anatomy and present auditory nerves. Those who do not have a connexin 26 mutation or who have note had genetic testing, imaging certainly is indicated for preoperative planning.
A CT scan is helpful for looking at the bony anatomy to determine the size of the cochlea, abnormal balance orders, or small channel through which the hearing nerve travels. Common inner ear abnormalities that are found include large vestibular aqueduct or a small cochlea such as Mondini malformation. Other than exceptional circumstances where the anatomy is severely affected, these bony abnormalities found on CT scans are not contra-indications for surgery and most children with mild to moderate inner dysplasia can be very success cochlear implant users and achieve significant improvement in sound and speech perception.
For those born with complete or profound hearing loss and no responses on auditory brainstem response (ABR) testing or behavioral testing, or if CT imaging suggests small or absent auditory nerve based on the size of the internal auditory canal or the cochlear nerve canal, a high resolution CT scan performed at the MEEI is important to determine the presence of absence of the auditory nerve itself. That nerve travels from the cochlea (inner ear) to the brain. That nerve should be present to provide the ability of the cochlear implant to electrically stimulate the inner and allow the signals to be sent along the nerve to the rest of the brain. In rare cases an auditory nerve is found to be very deficient or absent on MR imaging. Although this is not an absolute contra-indication to cochlear implant surgery, pooled data on cochlear implant outcomes in children with severely deficient or absent auditory nerves suggest that the overall performance is quite modest compared to those who have a near-normal to normal auditory nerve. These children appear to have some degree of sound awareness, but no true speech perception.
For more information about cochlear implants, please speak with your physician, or call the Infirmary's Audiology Department at 617-573-4047.
Information source: Mass. Eye and Ear