“Hearing with the Brain,” the topic of the Eye & Ear Foundation’s March 10th webinar, discussed hearing loss and research being done on cochlear implants.
Prevalence of Hearing Loss
“Hearing loss is an incredibly common problem,” said Andrew McCall, MD, FACS, Associate Professor of Otolaryngology at the University of Pittsburgh School of Medicine. In 2011, the estimated number of Americans with hearing loss was 48,000,000, or 20 percent of the U.S. population. While this data is from 10 years ago, it is still relevant today.
Some more statistics that emphasize the prevalence of hearing loss:
- 1/1000 newborns have hearing loss
- 1/3 of people over age 60 have hearing loss
- 1/2 of people over age 85 have hearing loss
Living, Diagnosing, and Treating Hearing Loss
What does it mean to live with hearing loss?
- Missing others talking
- Trouble understanding speech
- Asking others to repeat themselves
- Difficulty hearing speech in noise
- Problems with localizing sound
- Social isolation
- Dangerous situations
In terms of diagnosing hearing loss, testing for word understanding is a standard portion of audiometric testing, Dr. McCall said. An audiologist will say, “Say the word___.” Examples given were base, cab, cause, chat, and cheek.
Sensorineural hearing loss – which was the focus of today’s presentation – has several causes:
- Age-related hearing loss
- Noise-induced hearing loss
- Genetic hearing loss
Treatment involves lifestyle modification, hearing aids, assistive listening devices, and cochlear implants. Hearing aids come in different shapes, sizes, and functionality. They generally do a good job of helping people hear, especially when they have word understanding, Dr. McCall said. There are still challenges, however, such as understanding speech in situations with background noise. This may have something to do with how our brain processes sound.
Cochlear implants involve placing an electrode into the cochlea to electrically stimulate the nerve to the brain. Candidates for cochlear implants typically have:
- Bilateral moderate-to-profound sensorineural hearing loss
- Little/no useful benefit with appropriately fit hearing aids
- Poor word understanding on standardized cochlear implant pretest sentence testing in quiet and noise
Most insurance criteria require <50% score on the ear to be implanted and <60% in the best aided conditions.
Cochlear implants have been amazing for the vast majority of people with severe to profound hearing loss, Dr. McCall said. They do quite well and hear much better. There is a spectrum, however. Some people do not get much out of it at all. Many factors play into these differences.
Dementia and Hearing Loss
Dementia is associated with hearing loss. Of the potentially modifiable risk factors for developing dementia, hearing loss is the highest at eight percent.
“There is a lot to be learned about how the brain processes sound,” Dr. McCall said. “Maybe we can intervene clinically with patients to try to make their lives better.”
Michele Insanally, PhD, Assistant Professor of Otolaryngology at the University of Pittsburgh School of Medicine, and a Pittsburgh Hearing Research Center member, provided an overview of some translational projects she is working on in the lab. First, she answered the questions: How do we hear? How do we interpret what we hear? It is our brain that perceives sound and interprets their meaning, she said.
Dr. Insanally shared some quick statistics about hearing:
- 15% of American adults have trouble hearing
- 3 out of every 1,000 children in US are born with hearing loss
- Age is the strongest predictor of hearing loss
- 13% or 30 million people in the US aged 12 years or older have hearing loss in both ears
Her studies – which look at the neural basis of cochlear implant use — involve several things:
- Need for animal model of deafness and implant use
- Procedures for training rats to hear with cochlear implants
- Neural recordings
The Insanally Lab is working to understand how cochlear implants can affect other areas of the brain and how they can be adapted to more closely replicate how humans hear naturally.
Lots of work is being done to try to figure out if the association of hearing loss and dementia depends on the cause of hearing loss. As for whether a hearing aid or cochlear implant helps delay or prevent dementia in adults with moderate to severe hearing loss, that is the $1,000,000 question, Dr. McCall said. Studies are somewhat conflicting, but people are trying to figure this out and we will hopefully know in the coming years.
Dr. Insanally said in the short-term, instead of using patient self-reported sound quality, an audiologist will be able to send an EG signal to help program the cochlear implant. Certain patterns of brain activity will be indicative of optimal performance. Long-term, the goal is to create an implant that does something similar in real time.
Both presenters were asked what they are hopeful for when it comes to the future of cochlear implant technology. Dr. Insanally said, “I believe in a world where I will be able to fully restore hearing – something that at least approximates normal hearing levels.” She also hopes to improve learning rates, something being studied directly in the lab that could be moved to the clinic.
“I think science is fascinating,” Dr. McCall said. He talked about the cochlear implant as being a beautiful example of the amalgamation of technological advancement and understanding of neuroscience. Before the first cochlear implant decades ago, there was effectively no option for people with severe to profound deafness who did not benefit from hearing aids. Cochlear implants started off with one electrode, and now there are many. They used to be just for people with profound hearing loss, and now people with residual hearing or one-sided hearing loss are being implanted.
“The sky is the limit,” Dr. McCall said. “I remain optimistic that our scientists here are going to advance that knowledge so we can take it to the next level and help more and more people with implantable prostheses and other interventions to help the world hear better.”