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What Is Sensorineural Hearing Loss?
Sensorineural tissues in the inner ear have a very limited repair capacity. When hair cells are destroyed, the damage is permanent. But there are a number of ways audiologists can help you improve the experience of having SNHL.
Hearing AidsHearing aids are the most common way to address unilateral and bilateral hearing loss. They work by converting sound into electrical energy, which is amplified, transformed into an acoustic signal and reproduced by a speaker in the ear canal. Over the last few decades, hearing aid technology has advanced significantly, improving both sound clarity and comfortability.
As of October 2022, the Food and Drug Administration (FDA) allows the purchase of over-the-counter (OTC) hearing aids, which do not require a medical exam or a device fitting with a hearing health professional. However, it's still advantageous to see an audiologist before buying hearing aids.
During an audiogram, your provider determines the type and amount of hearing loss you're experiencing. If they recommend hearing aids, they also set the devices to prescriptive targets based on your hearing levels.
"Much like glasses, this prescription allows the hearing aid to provide support where the person needs it and not where they don't," says Dr. Osborne.
However, unlike eye glasses, "hearing aids are not an 'automatic fix' for hearing," explains Dr. Osborne. "It takes time for the brain to get used to hearing through the amplification, as well as for the patient to get comfortable wearing them and caring for them daily. But it can be compared to any new skill: The earlier you start, the easier it will be."
Even if you think your hearing loss doesn't necessitate hearing aids yet, getting fitted sooner can reduce the risk of other potential health problems, such as dementia.
"Without amplification, the hearing nerves can degenerate due to lack of stimulation," says Dr. Osborne. "Once this happens, the nerves can no longer relay auditory information clearly—meaning that if left without amplification for too long, a person may be unable to benefit from hearing aids at all."
If further medical intervention is needed, your audiologist may refer you to another specialist to determine other factors that could be causing your hearing loss.
Cochlear ImplantsA cochlear implant is a surgically fitted device that converts sound from mechanical to electrical energy through the hair cells in the cochlea. Cochlear implants are exclusively for patients with SNHL.
One piece sits behind the ear, picking up sounds with a microphone. The internal piece, which is surgically implanted in the inner ear, sends signals to the auditory nerve, which sends sound impulses to the brain.
Many users of cochlear implants may feel that the devices don't provide an identical experience to natural hearing. At first, the sound may be perceived as mechanical or robotic. Perception can change over time, and eventually, many users stop feeling bothered by the artificial quality.
But there are also some considerable risks associated with cochlear implants, including surgical complications, as well as unpredictability of patient satisfaction. They're usually only recommended for patients with hearing loss so severe that hearing aids are not effective, says Dr. Lin.
"A candidate often has 0% to 20% word understanding, and the average cochlear implant user may expect about 65% word understanding," he adds.
SteroidsWhen it comes to sudden SNHL, there's the possibility of improving hearing loss by treating a patient with steroids. Researchers believe that steroid treatment improves hearing because of its ability to reduce inflammation and swelling in the hearing organs and stimulate immune response.
"This treatment is not guaranteed to be effective, and maybe 50% of patients don't receive significant benefit from it," says Dr. Lin. "If helpful, hearing may be expected to improve in the first few weeks of treatment."
Treatment should ideally be undertaken within the first month of experiencing sudden SNHL, says Dr. Lin. Steroids can be administered with an injection directly to the inner ear or orally in the form of a pill.
What Is Muffled Hearing? Symptoms, Causes And Treatments
Various causes of muffled hearing may either lead to temporary or permanent damage. "The etiology [or origins] will determine its course," says Dr. Sarow.
Temporary Muffled Hearing"A common cause of temporary muffled hearing is a blockage in the middle ear, typically due to fluid buildup from a cold, an ear infection or allergies," says Dr. Sarow. A middle ear infection known as otitis media can also lead to a temporary blockage in the middle ear, which can cause significant hearing loss if left untreated.
Ear wax buildup can contribute to blockages as well, but a removal procedure can help resolve the temporary muffling. The same goes for other blockages. "A healthy middle ear space is filled with air rather than fluid," says Dr. Sarow. "Once the fluid resolves, hearing is restored."
There are three types of hearing loss: sensorineural, conductive and mixed. Sensorineural, the most common type, occurs when inner ear hearing loss reduces one's hearing volume and degree of clarity. Conductive hearing loss affects the middle and/or outer ear. All types are prone to causing either temporary or permanent muffled hearing sensations.
Temporary muffling may also emerge with certain health conditions, including:
Loud noises are another common cause of temporary muffled hearing. Damage to sensitive parts of the inner ear can cause noise-induced hearing loss. "If you've been to a concert and left with ringing in the ears and muffled hearing, [these symptoms are] evidence of damage to your auditory system," shares Dr. Sarow. "Also known as a temporary threshold shift, this muffled hearing may resolve within 48 hours of the exposure." However, permanent damage may ensue in recurring cases or after just one high-intensity incident.
Other causes of temporary muffled hearing include sudden changes in altitude and air pressure (known as airplane ear) and bacterial infections caused by excess water retention in the ears (known as otitis externa, or swimmer's ear).
Permanent Muffled Hearing"A sudden and permanent change in hearing may be due to sudden sensorineural hearing loss or, in rare cases, a benign growth on the auditory nerve," says Dr. Sarow. She adds that a middle ear condition, such as an eardrum perforation that cannot heal, can also sometimes result in permanent muffled hearing. Eardrum (or tympanic membrane) perforation occurs when your eardrum ruptures, creating a hole between the middle and external ear.
Other causes of permanent muffled healing include exposure to gunfire or explosions and age-related hearing loss,such as presbycusis, she shares.
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How Does Hearing Work?
Sounds in the environment produce tiny changes in air pressure. The ears detect these changes and send the information to the brain for processing.
A person's sense of hearing is incredibly versatile. It can detect extremely quiet sounds, determine whether a noise came from far or near, and isolate a specific sound within dense background noise.
In the United States, 1 in 8 people aged 12 years and older develops hearing loss in both ears.
In this article, we explore the anatomy of the ear, describe how hearing works, and investigate common causes of hearing loss.
The ear has three main sections: the outer, middle, and inner ear. Each section serves a distinct purpose in hearing.
Outer earThe outer ear is the visible part, also known as the pinna. Its primary job is to collect as much sound from the surrounding area as it can.
External sounds then enter a thin passage called the ear canal.
Middle earThe middle ear amplifies incoming sound with the help of a thin membrane called the eardrum, or tympanic membrane.
The eardrum separates the outer ear from the middle ear and helps to transmit sound vibrations to the inner ear.
Three tiny bones, called ossicles, amplify the sound. The names of the ossicles are:
The eardrum vibrates when sound waves reach it. This vibration moves the ossicles, transmitting sound further into the ear.
Meanwhile, the Eustachian tubes are thin, mucus-lined passages that help maintain stable pressure in the middle ear. Stable pressure allows sound waves to transmit correctly.
These tubes connect the middle ear to the back of the throat. A person can "pop" their ears by forcing air into the Eustachian tubes.
Inner earAfter the ossicles amplify the sound waves, the vibrations enter the cochlea.
The cochlea is a small, curled tube full of liquid that sits in the inner ear. It has an internal membrane, called the basilar membrane, which is covered in hair cells. Sound causes the fluid to rise and fall, moving the hair cells up and down as they "ride the wave."
Each hair cell has stereocilia — tiny hair-like projections — along its top. As the hair cells move up and down, the stereocilia bump into the structures above them. The bumping causes them to bend, and this opens up ion channels, creating a signal that the ear delivers to the brain.
Higher and lower pitches of sound activate hairs in different parts of the cochlea. The brain gathers information about pitch from the position of the activated hairs.
The cochlea sends this information along the auditory, or cochlear, nerve. The signal reaches the medulla, which is part of the brain stem. The brain stem is the area of the brain closest to the back of the neck.
The auditory nerve also carries information from the brain to the cochlea. The fibers of this nerve help suppress distracting sounds, allowing us to concentrate on just one sound among many.
For instance, when we are having a conversation in a busy room, the fibers of the auditory nerve help us focus on hearing one voice while ignoring other sounds.
People refer to pitch as frequency and measure it in hertz. The higher the hertz, the higher the pitch of the sound.
Intensity is another word for loudness, and people measure it in decibels (db).
The human ear usually hears sounds that are 20–20,000 hertz. However, in perfect lab conditions, some people can hear sounds as low as 12 hertz or as high as 28,000 hertz.
Hearing ability varies significantly from person to person. It tends to decline with age, especially the hearing of higher frequencies.
Most everyday sounds are 250–6,000 hertz. However, the ears are most attuned to sounds of 2,000–5,000 hertz.
As for intensity: Humans can detect sounds of 0–140 db. A whisper is around 25–30 db, and conversations are usually 45–60 db. A chainsaw is about 120 db.
The sound of a jet taking off 25 meters away is around 150 db and would cause the eardrums to rupture.
The ears are also vital for maintaining balance. The inner ear contains the vestibular system, a part of the body that is largely responsible for spatial orientation and the coordination of movement as they relate to balance.
Three small, fluid-filled loops, called semicircular canals, sit just above the cochlea. One detects up-and-down movement, the next detects side-to-side movement, and the third detects tilting.
The fluid in the semicircular canals shifts when a person moves their head. These canals also contain thousands of tiny, sensitive hairs, which bend as the fluid flows past them. This bending relays information to the brain about the type of movement.
When a person spins around and stops suddenly, the fluid keeps moving for some time, continuing to push against the hairs. The hairs continue to send messages to the brain, so the brain assumes that the person is still spinning. This is dizziness.
A vestibule joins the semicircular canals and the cochlea. It contains two sacs, called the utricle and the saccule, which send the brain information about how the head is moving in relation to gravity and acceleration.
For instance, the saccule helps a person tell whether they are traveling up or down in an elevator and, more importantly, whether they are lying down or standing up.
Various health conditions, lifestyle factors, and injuries can cause hearing loss.
There are two general types. Conductive hearing lossoccurs when sound cannot travel through the outer and middle ear.
Fluid in the middle ear, an ear infection, a tumor, damage to an ossicle, and a buildup of earwax can each cause conductive hearing loss. This type is often treatable.
Meanwhile, damage to the inner ear leads to the most common form of permanent hearing loss: sensorineural hearing loss. Causes include aging, genetic diseases, and drugs that are toxic to hearing, called ototoxic drugs.
Some people have inner ear damage alongside problems with the conducting of sound. This results in what doctors call "mixed hearing loss."
A doctor may also refer to hearing loss as bilateral, affecting both ears, or single-sided, affecting one ear.
Below are several possible causes of hearing loss:
Learn more about hearing loss and deafness.
The ear canal secretes earwax, or cerumen. It helps protect the skin from drying out and keeps the ear canal clean.
Earwax also offers some protection against bacteria, insects, fungi, and water. Its antibacterial properties may stem from its slight acidity and the presence of lysozyme — an enzyme that breaks down bacterial cell walls.
The largest component of earwax is dead skin. It also contains hair and secretions from glands within the ear canal. Other components of earwax include fatty acids, alcohols, and cholesterol.
Find out what earwax color says about ear health.
The ears are an intricate, delicate part of the sensory system. They send signals to the brain to help the person hear and understand their physical position.
The ears transmit information so effectively that many people give the complex process of hearing little thought. However, prolonged or sudden exposure to loud sounds, aging, and smoking tobacco can each cause hearing loss.
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