Sensorineural Hearing Loss: Causes, Problems, and Brain Training
A hearing impairment can have a major effect on the quality of life and cause a range of problems. The condition often makes communication with others difficult and can also cause some embarrassing situations, as I know from experience. Some US scientists recently discovered that one type of brain-training game was helpful in improving hearing in a small group of people. Though more research is needed in order to find the most effective exercises for training the brain and to identify which types of hearing loss they best help, brain training offers hope for the future.
The term “hearing loss” refers to both partial hearing loss (impairment) and complete loss. My impairment became noticeable in my forties and is gradually getting worse. I wear hearing aids, which are helpful in certain situations. Understanding human speech can sometimes be a challenge, however, especially in environments that are crowded and noisy. I would love to train my brain to help my hearing.
How We Hear: A Brief Overview
Sound vibrations must travel through the ear in order to stimulate the auditory (or cochlear) nerve. The nerve then sends an electrical signal to the auditory centre of the brain, which creates the sensation of hearing.
The part of the ear that is visible from outside the body is known as the pinna or auricle. It serves to collect sound waves and funnel them into the ear canal, or the external acoustic meatus. The sound waves cause the eardrum or the tympanic membrane to vibrate when they reach it. The pinna, ear canal, and eardrum form the outer ear.
The vibrating eardrum causes three tiny bones in the middle ear to vibrate. These bones are called ossicles. The eardrum is attached to the first ossicle, which is known as the malleus or hammer. The malleus transfers the vibrations to the incus, or anvil. This transmits the vibrations to the last ossicle, which is called the stapes or stirrup. The middle ear is filled with air.
The stapes transmits vibrations to a membrane known as the oval window. This sends the vibrations into the fluid of the cochlea, or organ of hearing. The cochlea looks like a snail's shell from the outside.
The vibrating fluid in the cochlea stimulates the hair cells in the organ. The cells get their name from hair-like projections called stereocilia, which are located at one end of a hair cell. Two types of hair cells exist: outer ones and inner ones. The outer hair cells amplify sounds. The inner ones send nerve impulses along the auditory nerve to the brain. Specific hair cells respond to specific frequencies of sound vibrations.
Hearing loss may be caused by problems in the middle ear or by an acoustic neuroma on the auditory nerve. Both of these problems should be investigated before a diagnosis of sensorineural hearing loss is accepted, as they were for me. An acoustic neuroma is a benign (non-cancerous) tumour on the auditory nerve.
Sensorineural Hearing Loss (SNHL)
I have sensorineural hearing loss, which is the most common type of impaired hearing. The disorder involves a loss of hair cells in the ear (the “sensory” part of the disorder), a problem with the auditory nerve, or—rarely—a problem with the auditory processing area in the brain. More than one of these problems may be present in the same person. The problem is thought to be most often located in the inner ear where the hair cells and the start of the auditory nerve exist. Unfortunately, any hair cells that die aren't regenerated.
Known causes of sensorineural hearing loss include the following:
- exposure to loud noises or noise that lasts for a long time, which kills hair cells
- a genetic problem
- exposure to certain chemicals or medications
- certain diseases, such as meningitis, scarlet fever, mumps, and measles
- problems with blood vessels
- injuries to the ear
Impaired hearing is not inevitable after exposure to the factors listed above, but the risk is increased. Sometimes the cause of a patient’s sensorineural hearing loss is unknown. People with the disorder may have a decreased ability to hear all pitches of sound, but the ability to detect high pitched ones is most seriously affected.
An Audiologist Discusses Sensorineural Hearing Loss
An audiologist is a health care professional who diagnoses and treats hearing problems and refers patients to a specialist when necessary. An audiogram is a graph created via a hearing test. The sound frequencies in hertz are located on the X axis and the loudness in decibels on the Y axis. The higher the frequency of sound vibrations, the higher the pitch of the sound.
Hidden Hearing Loss
In some people, a condition known as hidden hearing loss may be either the sole cause or a contributor to the failure to interpret speech in a noisy environment. The condition was officially recognized in 2009. Even before 2009, audiologists had noticed that some people complaining of an inability to interpret voices in noisy situations had normal audiograms. The hearing impairment was hidden from the audiologist, but not from the person experiencing it.
Researchers have discovered that a particular nerve pathway is activated in a noisy situation. The failure of this activation interferes with hearing. Someone with hidden hearing loss has a normal audiogram because the test is performed in a sound-proof room. Based on my experience, the only sounds delivered to the headphones worn by the subject are one voice at a time speaking words at different volumes. In this situation, the nerve pathway for distinguishing voices in a noisy area is never needed, so its failure isn’t noticed.
Unlike the audiologist in the photo above, mine uses a highly computerized system to measure hearing loss. She also uses a computer to control some of my hearing aid settings.
Social Isolation Caused by Impaired Hearing
One of the major effects of significant hearing loss is social isolation. This can develop not only because the person is unable to understand what other people are saying but also because of embarrassing situations that can develop for the person with impaired hearing. Some potential problems are listed below. Unfortunately, I've experienced all of them.
- A hearing-impaired person may guess what someone has said from the limited amount of speech that is understood, the speaker's body language, the inflection of their voice, and context clues. The guess may be wrong, however, causing the person with hearing loss to respond inappropriately. This can make them appear unintelligent to others (to put it mildly).
- If a person with hearing loss answers a question that isn't heard properly, the answer may convey the wrong information to the questioner.
- Asking someone to repeat what they’ve said multiple times is often annoying for the speaker.
- Ignoring a greeting or comment because it isn't heard makes a hearing-impaired person appear rude.
- Missing certain events because they may cause potentially embarrassing incidents can lead to social isolation.
- Staying quiet in a social situation can make a hearing-impaired person seem boring to other people.
The problems may be exacerbated because hearing loss can be a hidden disorder. If hearing aids aren’t worn, if they are hidden by hair, or if they are the in-the-canal type, other people may not realize that a person has a hearing problem. An in-the-canal hearing aid fits almost entirely in the ear canal. A tiny knob to enable removal of the aid is all that's visible to the public, if they even notice it.
Other Potential Problems
Failure to understand instructions for procedures or news announcements on public transit vehicles and at stations can be inconvenient and embarrassing. If the instructions relate to safety, the inability to hear them can be dangerous.
Difficulty in understanding speech can impair work performance. In some cases, it can make the job impossible to do and force a person to look for alternate employment. This is especially sad if it's a job that they enjoyed or that offered great benefits.
Hearing problems can lead to depression in some people. Researchers have also noticed that there appears to be a link between hearing loss and dementia. This certainly doesn't mean that someone with hearing loss is destined to develop dementia. It may depend on the cause of the hearing disorder as well as other factors. The potential association between the two disorders is a concern, however.
Sensorineural, Conductive, and Mixed Hearing Loss
Revealing a Hearing Problem to Others
It’s hard for some people to share the fact that they have hearing loss. The problem shouldn't be embarrassing to disclose, but it sometimes is. I'm fairly comfortable revealing my hearing problem in writing or to people that I know well. I find it very hard to reveal the situation in person to relative strangers or to people that I've never met before, however.
Some people may guess that the person that they are talking to has a hearing problem, especially if the person frequently asks for sentences to be repeated or makes illogical responses to questions or comments, but this isn't always the case.
Some advocates for the hearing impaired—including ones with their own hearing problems—argue that hearing aids should be obvious to the public or at least not deliberately hidden. They also say that people should publicly admit that are having difficulty in understanding a comment or a conversation because of a hearing problem. Every hearing-impaired person should consider what is personally right for them, however. They have the right to keep their condition a secret if they wish.
A stigma is often attached to hearing loss, perhaps because the behaviour of someone with diminished hearing can sometimes give the impression of stupidity, rudeness, or social ineptitiude. Advocates say that if more people revealed the fact that they have hearing problems and asked for help when necessary, the stigma and any false impressions would be decreased or removed. This is something that I need to keep in mind with respect to my own situation and behaviour. I love the Maryam Jamei quote related to being hearing impaired that is shown below.
You have to say "No. I am going to be part of this world. This is where I belong."— Maryam Jamei
A Hearing-Impaired Person Offers Some Advice
Good hearing aids can be very expensive and are out of reach of some people's budget. In addition, although they can be helpful, the aids may not solve all of a person's hearing problems. Other techniques for improving hearing could be beneficial. Brain-training exercises may be one of these techniques.
Four US scientists have discovered some very interesting facts related to brain training and hearing loss. The subjects in the research project were older adults with hearing loss. The researchers divided the subjects into two groups, each consisting of twelve people. One group performed the following exercise.
The subjects were given a tablet with a blank screen that held an invisible shape in its memory. The people had to trace the shape on the screen with their finger, even though they couldn't see it.
The people wore headphones that played a specific sound to let them know that they were on the right path with their finger and a different sound as they veered away from the path. The difference in the sounds was subtle. The sounds were masked by background noise which was at approximately the same level as that found in a noisy restaurant.
A subject's brain had to separate the sounds from the noise and interpret them. As the person became more successful at doing this, the background noise was increased. This made the detection of the sounds more difficult and further challenged the brain.
The second group in the experiment heard nonsense sentences against a noisy background as they played a game. They were asked to remember the words that they heard and then identify them later.
Results of the Study
After the training was finished, the researchers explored the improvement in the participants’ ability to understand the human voice against background noise. It might be expected that the second group would do better in this assessment because they had to distinguish and memorize words instead of sounds during the experiment, but that’s not what the experimenters found.
After eight weeks of training the researchers found no improvement in the memory group’s ability to understand speech in a noisy situation. On the other hand, the subjects that listened to the sounds were able to distinguish twenty-five percent more words from background noise (on average) compared to their ability before the training. Two months after training ceased, however, the enhanced ability to understand speech had vanished. Continuous practice or a longer period of training may be necessary for success.
Harvard neuroscientists Dan Polley and Jonathon Whitton may have found a solution (to the problem of distinguishing speech from a noisy background) by harnessing the brain’s incredible ability to learn and change itself. They have discovered that it may be possible for the brain to relearn how to distinguish between speech and noise. And the key to learning that skill could be a video game.— Dana Boebinger, from The Conversation and the Smithsonian Magazine
Questions and Concerns
One of the researchers says that he isn't certain why the sound game was successful. Evidence suggests that musicians who practice regularly have a better ability to distinguish language from a loud background than non-musicians. The tablet experiment required subjects to distinguish sounds from one another, as musicians must do, which may have been helpful for their hearing. More research is needed to confirm this, however.
The number of people involved in the study was quite small and the people were all in the older age range. Older people often suffer from presbycusis, or age-related hearing loss, which is a type of sensorineural hearing loss. The kind of hearing problem experienced by the subjects in the experiment wasn't stated in the reports that I've read, however.
The results of another project involving more people and other age groups could be useful to examine. It's known that the processing of sound in older brains is less effective than in younger ones. This processing may have been helped in the experiment, although there was no evidence supporting this idea.
Brain training needs to be performed with younger brains as well as older ones. It also needs to be performed with people who have different degrees of hearing loss and—if this is known—who experienced hearing loss for different reasons in order to reach a definite conclusion about benefits of the tablet game.
Commercial Brain-Training Programs
Commercial computer games or training programs that claim to help the brain to distinguish words in noisy environments already exist. Anyone thinking of buying or subscribing to these games and devoting time to playing them should look for independent evidence supporting their benefits for hearing loss. As the quote below indicates, some evidence suggests that the training programs might be helpful. This help is by no means guaranteed, however.
The level of evidence for most training programs is generally rather limited. However, given a number of studies potentially suggesting benefit of various training programs, it is possible that an individual who is willing to make a commitment to regular training (defined by some as 30 minutes per day, 5 days per week, for at least one month) might obtain some benefit.— Colleen Le Prell, University of Texas at Dallas, via Reuters
Hope for the Future
Brain training sessions to improve the understanding of spoken words would be wonderful, especially if they’re easy to obtain and and free or inexpensive to use. They must be designed properly in order to offer hope of success, however, which is why research is so important.
If specific games or exercises had a reasonable chance of helping my hearing, I would certainly play or perform them. I’m sure many other people with hearing loss would do the same thing. I hope research continues and that games with a good success rate are created. I also hope that suitable games become available for the public as soon as possible.
Hearing and hair cells from the University of Wisconsin-Madison
Information about sensorineural hearing loss from the U.S. National Library of Medicine
Hidden hearing loss in young people from Scientific American
Effects of a video game on hearing loss from the Smithsonian Magazine
Brain training games may help older adults with hearing loss from Reuters
Changes in audio processing in older brains from Research Gate
Age-related hearing loss or presbycusis from the NIH (National Institutes of Health)
Being a musician can help you distinguish language in loud environments from McGill University Newsroom
Breaking the stigma of hearing loss from Psychology Today
© 2018 Linda Crampton