Cochlear implant candidacy guidelines have been expanded over the years to include adults and children with severe to profound hearing loss bilaterally who do not benefit from the use of hearing aid amplification.
Millions of children and adults across the world have taken advantage of cochlear implant technology and have been successfully implanted to improve their hearing and communication.
But, what about the millions more who have severe high frequency hearing loss who are not cochlear implant candidates but are still struggling to hear conversations, particularly in noisy environments? Because their low frequency hearing is “too good” to qualify them as a candidate for a traditional cochlear implant, they are stuck in the middle between hearing aids and cochlear implants.
Traditional hearing aids are not enough for a lot of people with severe high frequency hearing loss because they can not sufficiently amplify high frequency information for it to be discernible, especially in background noise.
These individuals have been left frustrated.
A solution has now emerged. It is called a hybrid cochlear implant. It is for those who do not benefit from a hearing aid, but are not quite a candidate for a traditional cochlear implant.
A recent NYU-led multi-center study implanted 50 adults with severe high frequency hearing loss with a hybrid cochlear implant. Their speech recognition scores were tested one-year post implantation, with 45 participants showing a significant improvement in hearing and speech recognition. None of the participants hearing or speech recognition was worse following implantation.
What is a Hybrid Cochlear Implant?
It combines two proven technologies, a hearing aid and a cochlear implant, into one device. It uses the acoustic amplification of the hearing aid to improve low frequency hearing, while using electrical stimulation of the cochlear implant to improve high frequency hearing.
Clinics have been creating their own form of a hybrid implant for years by using a cochlear implant with a shorter, partially inserted electrode array, and wearing an in-the-ear hearing aid at the same time. Now, companies have combined the two devices into one system and, as of 2014, it is approved by the FDA for use in adults.
How does a Hybrid Cochlear Implant Work?
The external processor of the hybrid cochlear implant picks up incoming sounds and transmits the low frequency information to a hearing aid, which amplifies the sound based on the wearer's low frequency hearing loss. The high frequency sound information is transmitted to the cochlear implant component of the device, which is then converted into electrical impulses stimulating the high frequency regions of the hearing nerve.
How is a Hybrid Cochlear Implant Different from a Cochlear Implant?
A hybrid cochlear implant differs from a traditional cochlear implant in that it's electrode array is much shorter (less than 2 cm). With the electrode array being shorter, it does not go as far into the cochlea of the inner ear, only providing electrical stimulation to the high frequency sounds, leaving the low frequency hearing region undisturbed to preserve low frequency residual hearing.
A traditional acoustic hearing aid is then coupled with the processor of the implant to provide amplification to low frequency sounds as needed.
Who is a Hybrid Implant for?
A hybrid cochlear implant is for those with a severe to profound high frequency hearing loss with intact or moderately impaired low frequency hearing. Age-related hearing loss (presbycusis) and noise-induced hearing loss are the most common causes of sensorineural hearing loss, and almost always result in a high frequency hearing loss.
The hearing loss is caused by damage to the inner hair cells in the cochlea. The high frequency inner hair cells are more susceptible to aging and noise effects, resulting in that common high frequency hearing loss configuration. This has often been referred to as “nerve damage”, although that term is very misleading, as the hearing nerve remains intact.
The loss of high frequency hearing causes difficulty with speech recognition, especially in background noise. It can severely affect an individual's social and work environments and can lead to isolation and depression. The high frequency sounds create clarity of speech. When you are unable to hearing those high frequency consonant sounds, words can be difficult to distinguish and sound muffled.
Stuck in the Middle No More
There are currently two cochlear implant manufacturers that are now offering a hybrid implant system, Cochlear and MedEl.
Those with high frequency hearing loss who do not benefit from traditional hearing aids now have options. A hybrid cochlear implant uses “hybrid hearing” from both acoustic and electric stimulation to help these people hear and communicate easier.
For more information check out the video below to see one woman's experience with a hybrid cochlear implant: