Millions of people have some form of diminished hearing, but not all hearing loss is the same. The two main types—conductive and sensorineural—have different symptoms, underlying causes and recommended treatments. But what’s the difference?
Conductive Versus Sensorineural
The primary difference between conductive and sensorineural hearing loss is the part of the ear affected. Conductive hearing loss is rooted in an injury or illness in the outer and middle ear, whereas sensorineural hearing loss is due to a problem in the inner ear.
The second difference is how sound is perceived. People with conductive hearing loss hear less sound. For those with sensorineural hearing loss, sounds are not only diminished but also muffled or warped.
Conductive Hearing Loss
Conductive hearing loss occurs when something is wrong with the ear’s conduction mechanism, i.e., the outer and middle ear.
These two parts play an important role in channeling sound across the eardrum to the inner ear, where they are converted into bioelectrical signals.
In conductive hearing loss, there is a physical barrier blocking the transmission of sound across the ear. This could be earwax, fluid or foreign objects. It could also be the case that the ear itself is misshapen or malformed due to trauma or a genetic condition, so it might not funnel sound to the eardrum the way nature intended.
Damage to the tympanic membrane due to ear infections, or otitis media, can also affect the transfer of sound waves.
Sensorineural Hearing Loss
Sensorineural hearing loss involves a pathology beyond the tympanic membrane in the inner ear.
In addition to parts of the ear, nerve endings or the brain might be at fault. For people with sensorineural hearing loss, sounds are fainter and also distorted.
Loud noise and trauma can damage these delicate cells, impacting your hearing ability.
Sensorineural hearing loss can be caused by a tumor in the cochlear nerve or the erosion of its myelin sheath due to conditions like multiple sclerosis or syphilis. Damage to the brain due to a tumor or injury can also affect the processing of the signal in the auditory cortex of the brain.
Sensorineural hearing loss is the most common type of hearing loss, accounting for the majority of cases globally.
Mixed Hearing Loss
Some people experience both kinds of hearing loss at the same time. This is called mixed hearing loss.
It’s a combination of damage to the inner ear caused by loud noises or infection and blockage, injury or deformity of the outer and middle ear.
Mixed hearing loss usually occurs when there is a confluence of factors that contribute to other types of hearing loss. For instance, a person with age-related hearing loss might start wearing hearing aids, but they aren’t cleaned and fitted correctly, leading to earwax buildup and conductive hearing loss.
Testing for Conductive and Sensorineural Hearing Loss
Because sensorineural and conductive hearing loss have peculiar root causes and symptoms, they require different tests.
Your doctor may order a battery of tests to pinpoint the precise location of the pathology or rule out certain conditions. This is necessary for people who experience mixed hearing loss where elements of both types manifest.
Outer and Middle Ear Testing for Conductive Hearing Loss
The first step for both types of hearing loss is a hearing test and ear exam. Doctors will use an otoscope with a light at the end to look for earwax and foreign objects inside the ear canal.
They may also use a pneumatic otoscope that sends puffs of air to check the vibration and movement of the tympanic membrane. Tuning fork tests like Rinne’s and Weber’s are also done.
If your ENT observes little or no movement in the eardrum, they might recommend tests targeting the middle ear, like tympanometry, which involves inserting a tiny probe into the ear canal. An audiologist will send air into the ear canal and record the findings on a tympanogram machine.
This provides valuable diagnostic information about whether the eardrum is moving correctly. It can also detect earwax deposits, holes in the eardrum, signs of infection or a fluid buildup. All of this information helps diagnose conductive hearing loss.
The acoustic reflex measure is another test for the middle ear. Like tympanometry, this also entails sending a probe into the middle ear.
An acoustic reflex is when a tiny muscle contracts inside the ear in response to a sound.
Audiologists play sounds at different decibels to observe when your reflex reaction is triggered. This is an excellent test to determine how well you hear.
Finally, there’s the static acoustic impedance test. This test determines how much air is present in the ear canal. It can reveal if excess fluid is collecting beyond the eardrum.
Inner Ear Testing for Sensorineural Hearing Loss
Different tests are needed to evaluate the inner ear and the pathways beyond. Pure tone audiometry sends tones to the ear via the air and through the bone to test the patient’s relative sensitivity.
Doctors will use speech testing to determine what percentage of the speech is understood.
The speech reception is 50 percent in people with normal hearing, meaning they hear 50 percent of speech above 40 decibels.
Some ENTs may ask for videonystagmography (VNG) of the vestibular system in the inner ear. People with a vestibular problem often have a vision disorder called nystagmus, which shows up on VNG. An eye exam might be done simultaneously when vestibular conditions are suspected.
Doctors will sometimes order imaging like MRI and CT scans if they suspect tumors in the brain or along the auditory nerve.
Diagnosing Sensorineural and Conductive Hearing Loss
Although your doctor may already have a good grasp on the pathology behind your hearing loss, they may still test your entire hearing pathway. While you might feel this is unnecessary, it’s essential to rule out major life-threatening pathologies like cancer.
A clinical diagnosis is usually possible for both sensorineural and conductive hearing loss. However, in many cases, they may not find the cause. Diagnosing a processing problem in the brain can be difficult, and there are still disagreements in the medical community that need to be resolved.
Potential factors contributing to hearing loss include:
- Viral and bacterial infections
- Metabolic conditions, like low oxygen levels, high bilirubin levels
- Exposure to toxic amounts of chemicals like alcohol and thalidomide
- Trauma from birth, like bleeding and skull damage
- Syndromic and non-syndromic genetic conditions
- Exposure to street drugs like cocaine and heroin
- Exposure to industrial solvents
- Exposure to ototoxic medications
- Nutritional deficiencies of folic acid and Vitamin B12
- Paraneoplastic conditions
This is just a partial list. A whole range of tests is required to check levels in your blood, urine, and skin. Even with the extensive diagnostics available, about 71 percent of cases remain undiagnosed and are labeled idiopathic.
Conductive And Sensorineural Hearing Loss Prevention
To guard against both kinds of hearing loss, doctors recommend a set of basic preventive measures that help ensure your ears stay healthy as you age.
Preventing Conductive Hearing Loss
Now that you know the causes of conductive hearing loss, here are some steps to prevent it:
Manage Earwax Buildup
Clean your ears regularly to remove excess earwax and prevent blockage. Use medicated drops and warm water instead of cotton swabs, which can push earwax deeper into the ear canal, causing impaction.
Finally, keep headphones and earbuds clean and avoid using them continuously for long periods.
Treat All Ear Infections
If you develop a cold or infection that causes congestion in your ear canal and sinuses, don’t ignore it. Consult a doctor, who may prescribe antiviral or antibacterial medications.
If you don’t get medical help in time, the infection could damage the eardrum or cause pus and dead bacteria to accumulate, impeding sound. If an infection damages your eardrum, it must be reconstructed through costly surgery.
If your conductive hearing loss is caused by a congenital deformity of the outer ear, this could be corrected by reconstructive surgery. Ask your doctor about your surgical options.
Preventing Sensorineural Hearing Loss
Here are some things you can do to protect yourself against sensorineural hearing loss:
Limit Exposure to Loud Noise
Sounds louder than 85 decibels can damage the ear, contributing to sensorineural hearing loss.
An ambulance siren produces 125 decibels, and a rock concert is even louder. Even everyday noise like traffic can be harmful over time.
Wear Protective Equipment
Sometimes people can’t avoid noise because of their occupation. Use OSHA-approved earplugs or earmuffs if you work in a noisy setting like a construction site or a factory.
Rock musicians and frequent concert-goers should invest in specialized ear protection that allows you to hear the music without risking hearing loss.
Restrict Headphone Use
Exercise caution if you frequently use headphones to listen to music. Avoid continuous use at high volumes for long periods. Give your ears a break and follow what audiologists call the “60/60 rule.” Listen to your media at 60 percent volume for no longer than 60 minutes at a time. Also, regularly schedule hearing tests.
Maintain Good Health
Your hearing is tied to your overall health. Various chronic conditions can affect the blood vessels in the ear. A healthy diet and exercise staves off many of the cardiovascular and metabolic disorders that contribute to hearing loss. This keeps your blood vessels and nerves healthy.
You can’t prevent aging and age-related hearing loss, but using hearing aids and taking your medications as prescribed will help stave off dementia, thyroid complications, and other chronic conditions.
Use Hearing Aids Correctly
If you’re already wearing hearing aids to address sensorineural hearing loss, you need to adopt best practices to avoid making the problem worse.
Hearing aids that are incorrectly configured could amplify sound more than necessary, causing further damage. Consult an audiologist to ensure your hearing aids are appropriately fitted and programmed.
Treating Conductive And Sensorineural Hearing Loss
The treatment of hearing loss depends on the cause. If the cause of your hearing loss is unknown, physicians will treat you by trial and error. The therapy will be adjusted according to the relief it provides.
Conductive Hearing Loss Treatment
Treatment of conductive hearing loss focuses on improving conduction or amplifying the signal. Depending on the diagnosis, typical non-invasive treatments include:
- Cleaning your ears
- Taking antibiotics and antivirals for infections
- Wearing ear protection while swimming
More serious conditions like growths and exostoses could require surgery.
If the cause of your conductive hearing loss is a hole in the tympanic membrane less than 2 centimeters, it will generally heal by itself, but it may require minor surgery to repair. Otosclerosis, a common cause of hearing loss in young people, can be corrected by a surgical procedure called stapedectomy.
In some cases of conductive hearing loss, a hearing aid can be used to bypass the tympanic membrane. Assistive technologies can also amplify the sounds for people with conductive hearing loss.
Sensorineural Hearing Loss Treatment
The difference between conductive and sensorineural hearing loss is that the treatment of the latter is more complex. When the hair cells are damaged or degraded, background noise isn’t filtered properly, so it’s essential to boost the signal-to-noise ratio.
Hearing aids and cochlear implants are the first treatment options.
If the root cause of the hearing loss is a nerve disease, doctors might prescribe immunosuppressants, steroids, and monoclonal antibodies. Though there isn’t much evidence attesting to their effectiveness, vitamin B12 and folic acid supplements are sometimes recommended.
In severe sensorineural hearing loss, various communication therapies are recommended, such as speech reading, palm to print, and behavioral therapies.
People with hearing loss are also taught various coping methods, like reorienting their body’s position toward the speaker, having conversations in quiet places, and using FM installations where possible.
Audiology tech is progressing quickly, greatly expanding the types of treatment available.
Hearing loss is defined based on the physical location of the root cause and how it manifests. Whether you’re experiencing conductive, sensorineural or mixed hearing loss, it’s an impairment that dramatically reduces your ability to communicate and function in the modern world.
The good news is that advances in audiology and medical understanding of hearing loss equip healthcare providers with the tools to help most people with hearing problems lead a normal life. Prevention is your first line of defense, followed by rapid detection and treatment.
As you age, you need to be more aware of changes in your hearing ability. Get a hearing test regularly, and pay attention to feedback from others. If friends or family members tell you that you’re talking too loudly or that the volume on your TV is too high, the chances are that you could be experiencing hearing loss and need to take action to prevent it from getting worse.
Liu CM, Lee CT. Association of Hearing Loss With Dementia. JAMA Netw Open. 2019;2(7):e198112. Published 2019 Jul 3. doi:10.1001/jamanetworkopen.2019.8112