COVID-19: hearing loss, tinnitus and vertigo

Can COVID cause hearing loss?

The term "COVID ear" is becoming more common and may indicate a genuine medical condition. It's well-established that COVID-19 can lead to smell loss, known as anosmia. But could it cause hearing loss, tinnitus, or dizziness? Some suggest that sudden hearing loss, an infrequent yet often severe decrease in hearing, might be linked to COVID infection or even the COVID vaccination. Is this true? These are frequent questions I've encountered over the past pandemic years while treating patients with various cochlear and vestibular disorders. This post aims to tackle these questions by summarizing the latest scientific studies.

The short answer is, yes. The long answer is that there are different types of hearing loss associated with COVID, and that the severe ones are relatively rare. Fortunately, the chances of recovery for the most common type are generally positive.

• The first type of hearing loss is mechanical, called conductive hearing loss. It’s probably the most common form of hearing loss associated with COVID – and luckily the most benign. It’s caused a serous effusion (otitis media with effusion), which is fluid build-up behind the eardrum caused by the excessive mucus production and mucus membrane swelling. We see this commonly with viral upper respiratory tract infections (called URTIs). It’s the “stuffed ear” most of us already experienced at one point in our lives when we have a cold. It’s not dangerous, and usually spontaneously resolves in a few weeks, but can take up to a few months. If it fails to resolve on its own, your local ENT specialist can drain it with a minor intervention in the office called a myringotomy and tube placement.
  
  
• The other type of hearing loss associated with COVID is called

   sensorineural hearing loss and suggests damage to the inner ear structures or to the hearing-balance nerve by the COVID-19 virus. Infection of the inner ear by COVID-19, or other viruses, can lead hearing loss, tinnitus and vertigo/dizziness. The hearing loss can be in one or two ears, and range in severity from mild to moderate to severe. Hearing loss is rarely the first sign of a COVID infection (unlike smell loss which occurs early on) and usually occurs later in the disease, but it has been reported to be the only symptom in one study (see Reference 1 below).

 

• More importantly - and more seriously - COVID infection might also present as sudden sensorineural hearing loss: a hearing loss that occurs rapidly in one (rarely two) ears, and can be non-reversible. It is therefore important to consult your local physician and arrange for an urgent hearing test (audiogram) if you suspect having a sudden drop in hearing. 
  
  

Treatment for sensorineural hearing loss in the context of COVID infection is usually with oral prednisone or through ear injections, although spontaneous recovery can be seen in up to one third of patients. The faster you start treatment, the higher your chances of recovery. So when in doubt, get your hearing tested.

How common is hearing loss with a COVID infection?

With the benefit of hindsight, a few years after this pandemic, we now have a clearer perspective. The largest study on the topic was published in early 2021, and was a systematic review of 56 studies that published on the topic (see Reference 2 below). Their summary indicated that, overall:

• Hearing loss was reported in 7.6% (up to 15.1%) of patients
  
  
• Tinnitus was reported in 14.8% (up to 26.1%)
  
  
• Vertigo was reported in 7.2% (up to 26.4%).

It is important to note that the quality of some of the 56 studies published was limited: some did not mention whether the hearing loss was sensorineural or conductive while others did not formally test the hearing or the balance function, or even the COVID-19 status. It is therefore hard to determine exactly how often ear and balance symptoms occurs, but having this range is helpful when counselling patients.

What about tinnitus and vertigo?

These two symptoms are harder to test and therefore more challenging to study. Researchers typically rely on self-administered patient surveys to estimate how common and severe they are.

Tinnitus

As we mentioned in the section above, tinnitus was the most common reported ear symptom in patients suffering from COVID, affecting on average 14.8% of them. In these patients, the tinnitus was typically described as non pulsatile (similar to “white noise”), although some patients mentioned it being pulsating. Complicating the matter even more, tinnitus can happen with or without hearing loss. It usually lasted days to weeks, although some studies mentioned a tinnitus that persisted. Tinnitus was more common in people that already suffered from tinnitus before the pandemic, and in those individuals, a COVID infection usually worsened their tinnitus. Because we don’t really understand the pathophysiology of tinnitus, it’s hard to know whether the virus itself is the cause of the tinnitus, or whether other factors came into play (social isolation from lockdowns, stress related to the pandemic, etc.). We currently do not have an effective treatment to cure tinnitus.

Vertigo

Vertigo was the least common of the ear-related COVID symptom (7.2% of patients). According to the large study by Monro and colleagues cited above, vertigo due a COVID infection can manifest as a spinning sensation lasting minutes to hours or days, or it can present as a sensation of dizziness.

Spinning vertigo is what we, as neuro-otologists, consider true vertigo in the sense that it is likely of vestibular origin, i.e. the inner ear is the cause. A COVID-induced vestibular neuritis, a condition in which there is inflammation of the balance nerve, would be an example of such vertigo. The severe vertigo usually resolves on its own in a few days, but the balance may take a few weeks to return to normal. It can be treated with prednisone as well.

When COVID-related vertigo can present as dizziness, it is typically described as a sensation of swaying, rocking or imbalance.

Scientific proof: COVID-19 virus can infect the inner ear

We’ve known for years that certain viruses can damage the inner ear: Cytomegalovirus (CMV) and Rubella for example, are known to cause deafness at birth by causing irreversible damage to the cochlea.

For the first time however, a group of researchers from MIT (see Reference 3 below) was able to demonstrate that the COVID-19 virus can in fact penetrate the inner ear cells. The researchers used an animal and reconstructed human inner ear model for their study, so not in a real live ear. Still, by proving the COVID-19 virus could penetrate inner ear cells, they provide a scientific explanation for the sensorineural hearing loss, tinnitus and loss of balance in patients infected with COVID-19.

How the COVID virus damages the inner ear is still unknown. We know COVID-19 can reach the middle ear and mastoid bone (the bone that contains the ear organs): researchers used autopsy specimens from patients who died from COVID to confirm this (see Reference 4 below). How it spreads from the middle ear to the cochlea (to cause the sensorineural hearing loss) is still unknown however. Some studies showed bleeding into the cochlea (the hearing organ) on MRI imaging. Others suspect it leads to a viral inflammation of the inner ear called labyrinthitis or of the hearing and balance nerve. The jury is still out and more research is needed.

Bottom line?

COVID infection can in fact cause hearing loss, tinnitus and vertigo, although these are not very common symptoms of the disease. The most serious form is sudden sensorineural hearing loss – a rapid and severe hearing loss – so when in doubt, consult your local physician and get your hearing tested: you may otherwise miss out on an opportunity to get treated and get your hearing back.