- New research suggests that the ear is yet another part of our bodies that is susceptible to infection with SARS-CoV-2, the virus that causes COVID-19.
- For this research, scientists developed novel cellular models of the inner ear and used hard-to-obtain adult human inner ear tissue.
- Researchers also found that the virus could infect two types of cells in the inner ear called Schwann and hair cells.
Hearing loss after COVID-19 has already been observed, but new research from the Massachusetts Institute of Technology (MIT) and Massachusetts Eye and Ear has been able to break down what is happening when the coronavirus attacks the inner ear.
The study, recently published in the journal Communications MedicineTrusted Source, analyzed cellular models of the human inner ear and adult human inner ear tissue with SARS-CoV-2 infection to discover what effect it might have.
Findings suggest that the ear is yet another part of our bodies that is susceptible to infection with SARS-CoV-2, the virus that causes COVID-19.
“This article provides very compelling evidence that SARS-CoV-2 infects the inner ear, and may be causally related to the hearing and balance symptoms in a number of patients with COVID-19 infection,” Dr. Yuri Agrawal, a professor of otolaryngology-head and neck surgery at Johns Hopkins School of Medicine, who was not involved in the study, said in a statement.
Findings could help us understand how SARS-CoV-2 and other viruses affect ear
For this research, scientists developed novel cellular models of the inner ear and used hard-to-obtain adult human inner ear tissue.
According to the study authors, limited availability of this tissue had hindered previous research into how SARS-CoV-2 and other viruses can damage hearing.
They found a pattern of inner ear infection consistent with symptoms observed in a study of 10 patients with COVID-19 who had reported a range of ear-related symptoms.
“Having the models is the first step, and this work opens a path now for working with not only SARS-CoV-2 but also other viruses that affect hearing,” Lee Gehrke, PhD, the Hermann L.F. von Helmholtz professor in MIT’s Institute for Medical Engineering and Science, who co-led the study said in a statement.
The study included 10 adult patients who tested positive for COVID-19 and developed symptoms that included hearing loss, tinnitus (ringing in the ear), or dizziness within 3 weeks of diagnosis.
Researchers analyzed inner ear tissue sourced from humans and mice to create in-vitro cellular models of the inner ear.
They discovered that both human and mouse inner ear tissue contained “molecular machinery to allow SARS-CoV-2 entry,” like the ACE2 receptor. Researchers also found that the virus could infect two types of cells in the inner ear called Schwann and hair cells.
“Our findings suggest that inner ear infection may underline COVID-19-associated problems with hearing and balance,” the study authors wrote.
Schwann and hair cells play vital roles
“Vestibular hair cells serve as sensory receptors in the inner ear that function to assess and monitor head motion, a sense of balance, allowing humans and animals to orient themselves,” Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York, told Healthline.
“Schwann cells, also found in the specialized apparatus of the inner ear known as the cochleaTrusted Source, are vital to hearing,” he continued.
According to Glatter, the takeaway is that this study found that vestibular hair cells and Schwann cells express proteins that are essential for SARS-CoV-2 to enter cells.
“These proteins include the ACE2 receptor, which is found on the surface of cells,” he said, “and two enzymes called furinTrusted Source and transmembrane protease serine 2 (TMPRSS2)Trusted Source, which allow SARS-CoV-2 to attach to the host cell.”
Different infections passed from mother to baby can cause deafness
According to the study authors, the developing inner ear is “notoriously sensitive” to congenital (born with) viral infection, and congenital cytomegalovirus (CMV)Trusted Source accounts for many cases of hearing loss at birth.
“Viruses such as CMV as well as HIV can lead to hearing loss,” said Glatter. “CMV accounts for up to 40 percent of congenital hearing loss.”
He added that HIV could also lead to hearing loss “via direct effects on ear structures or specialized ear cells themselves,” or indirectly, by suppressing the immune response that protects against bacterial or fungal infection.
Researchers noted that they observed SARS-Cov-2 infection of OPCs, a cell type present in the developing fetal inner ear.
The Centers for Disease Control and Prevention (CDC)Trusted Source recommends that pregnant people get vaccinated against COVID-19 to prevent infection that could cause complications like this and others in newborns.
Glatter emphasized the need to pay “extra” attention to symptoms like dizziness, hearing loss, and tinnitus in those exposed to COVID-19, as well as those who test positive for the coronavirus.
“While fever, loss of taste and smell, and respiratory symptoms may be more common in those ultimately diagnosed with COVID-19,” said Glatter, “neurological presentations including dizziness, hearing loss, vertigo, and stroke-like symptoms can also be important presenting symptoms of COVID-19.”
Some people with long COVID, also known as long-haul COVID-19, report dizzinessTrusted Source and tinnitus among other symptoms long after their initial infection.
The bottom line
New research finds that cells in the ear are susceptible to infection with SARS-CoV-2, causing symptoms that include dizziness, ear ringing, and hearing loss.
Experts say that other viruses may also cause hearing loss, and newborns can be especially at risk.
They also say that while neurological symptoms of SARS-CoV-2 infection are less common, they’re still very important signs of disease that should be considered in those who test positive for, or are exposed to, COVID-19.
Your Inner Ear Explained
Your inner ear, also called the labyrinth, plays a key role in your hearing and sense of balance. Several conditions can impact the inner ear.
Your inner ear is the deepest part of your ear.
The inner ear has two special jobs. It changes sound waves to electrical signals (nerve impulses). This allows the brain to hear and understand sounds. The inner ear is also important for balance.
The inner ear is also called the internal ear, auris interna, and the labyrinth of the ear.
Inner ear anatomy
The inner ear is at the end of the ear tubes. It sits in a small hole-like cavity in the skull bones on both sides of the head.
The inner ear has 3 main parts:
- Cochlea. The cochlea is the auditory area of the inner ear that changes sound waves into nerve signals.
- Semicircular canals. The semicircular canals sense balance and posture to assist in equilibrium.
- Vestibule. This is the area of the inner ear cavity that lies between the cochlea and semicircular canals, also assisting in equilibrium.
Inner ear function
The inner ear has two main functions. It helps you hear and keep your balance. The parts of the inner ear are attached but work separately to do each job.
The cochlea works with parts of the outer and middle ear to help you hear sounds. It looks like a small spiral-shaped snail shell. In fact, cochlea means “snail” in Greek.
The cochlea is filled with liquid. It contains a smaller, sensitive structure called the organ of Corti. This acts like the body’s “microphone.” It contains 4 rows of tiny hairs that pick up the vibrations from the sound waves.
The path of sound
There are several steps that have to happen from outer ear to inner ear for a person to hear a sound:
- The outer ear (the part that you can see) acts like a funnel that sends sounds into your ear canal from the outside world.
- The sound waves travel down the ear canal to your eardrum in the middle ear.
- Sound waves make your eardrum vibrate and move the 3 tiny bones in your middle ear.
- The movement from the middle ear leads to pressure waves that make the fluid inside the cochlea move.
- The movement of fluid in your inner ear makes the tiny hairs in the cochlea bend and move.
- The “dancing” hairs in the cochlea convert the movement from sound waves into electrical signals.
- The electrical signals are sent to the brain through the hearing (auditory) nerves. This makes a sound.
Balance
The balance parts of the inner ear are the vestibule and the semicircular canals.
The 3 semicircular canals are loop-shaped tubes in the inner ear. They’re filled with liquid and lined with fine hairs, just like in the cochlea, except these hairs pick up body movements instead of sounds. The hairs act like sensors that help you with your balance.
The semicircular canals sit at right angles to each other. This helps them measure motions no matter what position you’re in.
When your head moves around, the fluid inside the semicircular canals shift around. This moves the tiny hairs inside them.
The semicircular canals are connected by “sacks” in the vestibule that have more fluid and hairs in them. They’re called the saccule and utricle. They also sense movement.
These movement and balance sensors send electrical nerve messages to your brain. In turn, the brain tells your body how to stay balanced.
If you’re on a rollercoaster or a boat that’s moving up and down, the fluid in your inner ears might take a while to stop moving. This is why you may feel dizzy for a little while even when you stop moving or are on solid ground.
Inner ear conditions
Hearing loss
Inner ear conditions can affect your hearing and balance. Inner ear problems that cause hearing loss are called sensorineural because they usually affect the hairs or nerve cells in the cochlea that help you hear sound.
The nerves and hair sensors in the inner ears can get damage due to aging or from being around too much loud noise for too long.
Hearing loss can happen when your inner ears can’t send nerve signals to your brain as well as they used to.
Symptoms include:
- muffled higher pitch tones
- difficulty understanding words
- difficulty hearing speech against other background noises
- difficulty hearing consonant sounds
- difficulty honing in on where a sound is coming from
Balance issues
Most balance problems are caused by issues in your inner ear. You may feel vertigo (a room spinning sensation), dizziness, lightheadedness, or unsteady on your feet.
Balance problems can happen even if you’re sitting or lying down.
Related conditions
Conditions in or adjacent to the inner ear can affect balance and may also sometimes cause hearing loss.
These include:
- Acoustic neuroma. This rare condition happens when a benign (noncancerous) tumor grows on the vestibulocochlear nerve connected to the inner ear. You may have dizziness, loss of balance, hearing loss, and a ringing in your ear.
- Benign paroxysmal positional vertigo (BPPV). This happens when calcium crystals in your inner ear move from their normal places and float around elsewhere the inner ear. BPPV is the most common cause of vertigo in adults. You might feel like everything is spinning whenever you tilt your head.
- Head injury. A head injury involving a blow to the head or ear can damage the inner ear. You might experience dizziness and hearing loss.
- Migraine. Some people who get migraine headaches also have dizziness and motion sensitivity. This is called a vestibular migraine.
- Meniere’s disease. This rare condition can happen to adults, typically between their 20s and 40s. It can cause hearing loss, vertigo, and tinnitus (ringing in the ears). The cause is not yet known.
- Ramsay Hunt syndrome. This condition is caused by a virus that attacks one or more cranial nerves near the inner ear. You may have vertigo, pain, hearing loss, and facial weakness.
- Vestibular neuritis. This condition, which may be caused by a virus, involves inflammation in the nerve that conducts balance information from the inner ear to the brain. You may have nausea and dizziness that’s so severe it makes it difficult to walk. Symptoms can last for days and then improve without any treatment.
Treating inner ear conditions
See a specialist
You may need to see a specialist called an ENT (ear, nose, and throat specialist) to get treatment for an inner ear condition.
Viral illnesses that affect the inner ear may go away on their own. Symptoms usually get better over time. In some rare conditions, your doctor may recommend other treatment like surgery.
Use hearing devices
Hearing aids, including implantable hearing aids, may help improve hearing in people with some hearing loss or deafness in one ear.
For people who have partial hearing intact there are also sound-boosting and focusing devices on the market.
Cochlear implants are kinds of hearing aids that help children and adults with severe sensorineural hearing loss. It helps to make up for damage to the inner ear.
Care for earaches
Home remedies may help soothe symptoms from earaches caused by a viral infection.
Some viral inner ear infections may get better without treatment. But they can sometimes affect hearing and balance for a little while.
Try at-home tips to help relieve pain and other ear symptoms such as:
- over-the-counter pain medications
- a cold compress
- heat therapy
- neck exercises
Ways to keep ears healthy
Clean your ears
Earwax can build up in your outer ear canal. This can affect hearing and may raise the risk of infection in your external auditory canal or potentially hurt your eardrum.
Earwax buildup to the point of impaction could also lead to hearing problems or dizziness. If you have a lot of earwax, see your doctor. A healthcare provider can provide ear cleaning at the doctor’s office.
Trying to clean your ears by yourself with a cotton swab can sometimes push the wax in deeper and overtime pack wax into your ear canal like a plug. This requires professional help to remove.
Read more on how to clean your ears safely.
Protect your ears
Protect your ears from sound just like you protect your eyes from the bright sun:
- Avoid listening to music or movies at a very high volume.
- Wear ear protection if you’re around loud or constant noises, like when traveling in an airplane.
The takeaway
The inner ear works with the outer and middle ear to help people hear.
It can change or be damaged from normal aging, loud noises, trauma, and illness. It plays a very important role in hearing and balance.