Hearing and COVID-19, what do we know?

I have been prompted to do some research because I have a friend who was recently diagnosed with Long COVID, and she asked me how it may impact her hearing. I needed a clear answer, so I turned to current publications to gather some information.

The COVID-19 virus has impacted us all, some more than others. Numbers of infections continue to be counted, and management/treatment is still evolving; the review of what has happened is being published in peer-reviewed literature. There are reports, from several sources, of hearing loss, tinnitus and dizziness. These otoneurological conditions include tinnitus and balance disorders, smell and taste disorders and sudden sensorineural hearing loss. The severity of the Covid infection does not appear to influence the otoneurological symptoms reported. One complication to this data is that many patients were isolated, on breathing equipment or critically ill and unable to provide illness history. The collection of accurate data has thus been impaired or delayed. As such, the reports may be conservative. The additional complication is that many clients' otoneurological baseline was unknown at the time of infection, so differentiating new from previous presentations is difficult. 

There are also some recorded incidents of the sudden onset of hearing loss post-vaccination, though these are rare. Following the case history of three patients that developed sudden sensorineural hearing loss (SSHL), the prompt treatment by consulted medical professionals did result in recovery (complete and partial) in two cases but had no impact on the third patient.

It is known that the inner ear and vestibular organs are vulnerable to viruses. As such, linking sensorineural hearing loss (SNHL), tinnitus and/or vertigo to COVID-19 (SARS-CoV-2) infection is not surprising. The proposed mechanisms of how/what damage is done to the sensory organs are hypoxia (lack of oxygen), immune-mediated damage (abnormal activity of immune cells), coagulative disorders (affects blood's clotting activities) and viral direct damage/invasion. 

Chemosensory impairment (impairment to taste and smell) is well documented among infected patients; The research has shown a relationship between a receptor of an enzyme and the binding of COVID-19 to human cells. These receptor cells are found not only in the respiratory tract but also in the Eustachian tube, middle ear and cochlear hair cells, thus suggesting these tissues are vulnerable to infection. 

The cochlear arterial supply is terminal, the only supply of oxygenated blood to the organ/tissue. A microvascular disorder related to infection/inflammation could cause sudden hearing loss. (indirect ischemic damage.) Some MRI data from patients also shows microhemorrhages, microvascular injury, congestion of blood cells and perivascular (fluid-filled compartments surrounding cerebral blood vessels) inflammatory infiltration. 

There is also discussion about the COVID-19 virus stimulating an autoimmune response, but this still needs to be debated. 

Some patients have presented to hospitals with life-threatening infections; treatments are still being tested and evaluated. Some medications given to patients may be ototoxic, which is toxic to the sensitive hearing system. Once they recover, they may have sensorineural hearing loss caused by the medication. 

There is documentation that some people post-infection report the onset of tinnitus, which may or may not be related to a change in hearing. Psychological triggers of tinnitus, particularly those exacerbated by the pandemic, such as loneliness, poor sleep, depression and anxiety, may play a role in inciting or worsening tinnitus. The one study I found did show that some medical intervention was helpful for the patient discussed. As for the underlying pathology, it is still very much up for research and discussion. 

So for my friend diagnosed with long Covid, what have I learned? I have learned that the incidence of hearing loss due to COVID-19 infection is possible but is not a widely reported symptom. If she has concerns, then a thorough hearing test is required. The collection of accurate hearing levels and looking at management, which may involve hearing aids or medical referral, as early as possible is related to improved quality of life. Long Covid is a multi-system condition and thus requires her to address her pre-existing conditions, respond to new needs and manage her energy, stress and mental health sensitively, to maintain quality of life. The current health services in Australia are still learning what will be needed and effective for Long Covid diagnosed patients.  

If you feel that your hearing might not be as good as it used to be, book an appointment to see an audiologist today. 

Louise Colclough

Senior Audiologist - Chatswood

https://www.valuehearing.com.au/staff/louise-colclough

Reference links

https://journals.sagepub.com/doi/pdf/10.1177/01410768211032850

https://www.sciencedirect.com/science/article/pii/S0196070921003094

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9219889/