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- A review of the published evidence revealed associations between SARS-CoV-2 – the virus that causes COVID-19 – and tinnitus, hearing loss and dizziness.
- Possible causes include infection of the nerves, autoimmune damage, and blood clots.
- The results are preliminary, as most reports of hearing and balance problems rely on patient questionnaires and medical records rather than diagnostic tests.
According to the UK’s National Institute for Health and Care Excellence, dizziness, tinnitus and ear pain are among the common symptoms of long-term COVID.
Other viral infections – including rubella, measles and cytomegalovirus – are known to cause hearing problems, but research into possible links between COVID-19 and hearing problems remains at an early stage .
In June 2020, specialists at the Manchester Center for Audiology and Deafness (ManCAD) in the UK reviewed seven studies suggesting a link between hearing and balance problems, or audiovestibular, and COVID-19.
At that time, however, the quality of the evidence supporting a possible association was poor.
The same researchers have now updated their review to include 56 studies published in 2020.
Although the evidence remains tentative, researchers have estimated the prevalence of audiovestibular problems in people who have recovered from SARS-CoV-2 infection.
Their analysis suggests that about 14.8% of patients suffer from tinnitus or “ringing in the ears,” 7.6% have hearing loss, and 7.2% have rotational vertigo, which is a sensation of spinning.
The journal appears in the International Journal of Audiology.
The authors point out that these numbers may overestimate the true extent of the problem.
This is because the reports they reviewed did not always make it clear whether the symptoms were new or whether they were pre-existing symptoms that had temporarily worsened.
Additionally, most studies relied on medical records or questionnaires in which patients reported their own symptoms, rather than the appropriate hearing tests.
“There is an urgent need for a carefully conducted clinical and diagnostic study to understand the long-term effects of COVID-19 on the hearing system,” says lead author Kevin Munro, professor of audiology at ManCAD.
“While this review provides additional evidence for an association, the studies we reviewed were of varying quality, so more work needs to be done,” he adds.
Professor Munro is leading a year-long study in the UK that will compare control patients to patients who have recovered after being hospitalized with COVID-19.
He and his colleagues hope to get a more accurate picture of the incidence and severity of COVID-related hearing problems, as well as which parts of the hearing system are affected.
They will also study possible associations between audiovestibular problems and other factors, such as lifestyle, other medical conditions, and the treatments patients have received in intensive care.
Professor Munro explains:
“Over the past few months, I have received numerous emails from people who have reported a change in their hearing, or tinnitus after having COVID-19. While this is alarming, caution is in order as it is not clear whether the hearing changes are directly attributed to COVID-19 or to other factors, such as treatments to provide urgent care. “
The inner ear contains the spiral sound-sensing cavity of the cochlea and the fluid-filled semicircular canals, which are involved in balance.
In their article, the researchers note some of the explanations offered for the damage to the inner ear that occurred when people had COVID-19.
These include:
- direct viral infections of the inner ear or the nerve that transmits sensory signals
- autoimmune attack by antibodies or immune cells, or damage caused by excessive production of cytokines, which are immune signaling molecules that cause inflammation
- blood clots that block the blood supply to the cochlea or semicircular canals, depriving them of oxygen
The authors conclude their article by urging caution when interpreting their estimates of the prevalence of hearing problems associated with COVID-19.
They write that some of the problems may have been pre-existing, pointing out that around 11% of the UK adult population already have hearing problems and 17% have tinnitus.
Additionally, they claim that in about half of the studies reviewed, they were unable to determine whether the authors were reporting a new symptom or a worsening of an existing symptom.
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