- SARS-CoV-2, the virus that causes COVID-19, has been linked to tinnitus, hearing loss, and vertigo, according to a study of published data.
- Nerve infection, autoimmune injury, and blood clots are all possible causes.
- Since most cases of hearing and balance issues depend on patient questionnaires and medical history rather than diagnostic testing, the results are preliminary.
Other viral infections, such as rubella, measles, and cytomegalovirus, have been related to hearing difficulties, but research into COVID-19 and hearing issues is still in its early stages.
Specialists at the Manchester Centre for Audiology and Deafness (ManCAD) in the United Kingdom reviewed seven studies in June 2020 that indicated a correlation between COVID-19 and hearing and balance problems, or audiovestibular problems.
However, the evidence suggesting a potential connection at the time was of low quality.
The same researchers have revised their study to include 56 studies that were released in 2020.
The researchers estimated the prevalence of audiovestibular problems in people who have recovered from a SARS-CoV-2 infection, despite the evidence being preliminary.
According to their results, 14.8 percent of patients have tinnitus, or ringing in the ears, 7.6 percent have hearing loss, and 7.2 percent have rotatory vertigo, or spinning sensations.
The journal International Journal of Audiology published the study.
The authors point out that these statistics may be exaggerating the true scope of the issue.
This is due to the fact that the reports they looked at did not always indicate if the symptoms were new or whether they were preexisting symptoms that had temporarily intensified.
Furthermore, rather than using accurate hearing tests, the majority of the research relied on medical reports or questionnaires in which patients recorded their own symptoms.
“A carefully performed clinical and diagnostic research is urgently needed to clarify the long-term effects of COVID-19 on the auditory system,” says senior author Kevin Munro, an audiology professor at ManCAD.
“Though this review provides further evidence for an association, the studies we looked at were of varying quality, so more work needs to be done,” he adds.
Prof. Munro is leading a year-long study in the United Kingdom that will compare control patients to COVID-19-hospitalized patients who recovered.
He and his colleagues want to learn more about the prevalence and severity of COVID-related hearing problems, as well as which areas of the auditory system are impaired.
They’ll also look at potential connections between audiovestibular issues and other factors like lifestyle, other medical conditions, and the intensive care services the patients got.
Prof. Munro explains:
“Over the last few months, I have received numerous emails from people who reported a change in their hearing, or tinnitus after having COVID-19. While this is alarming, caution is required, as it is unclear if changes to hearing are directly attributed to COVID-19 or to other factors, such as treatments to deliver urgent care.”
Potentially harmful factors
The spiral cavity of the cochlea, which senses sound, and the fluid-filled semicircular canals, which are involved in balance, are both located in the inner ear.
The researchers mention some of the proposed reasons for the damage to the inner ear that occurred in people who had COVID-19 in their report.
- direct viral infections of the inner ear or the nerve that carries sensory signals from it
- 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 advise readers to use caution when interpreting their estimates of the prevalence of COVID-19-related hearing problems.
They write that some of the issues may have been pre-existing, pointing out that about 11% of the adult population in the United Kingdom has hearing loss, and 17% has tinnitus.
Furthermore, they say that they were unable to decide whether the writers were documenting a new symptom or a worsening of an existing one in roughly half of the studies they looked at.