So far, there have been reports from COVID-19 patients of symptoms such as hearing loss, tinnitus, and drowsiness, which researchers say also affects the inner ear. Accordingly, dizziness and balance disorders can occur with corona infections, which suggests that SARS-CoV-2 can also infect this area. A new study provides evidence that coronavirus can actually affect hair cells. These are crucial for both hearing and balance.
How COVID-19 can endanger the inner ear
The researchers also found that a pattern of infection in human inner ear tissue was consistent with the symptoms seen in COVID-19 patients. To study Sars-CoV-2 infection in terms of hearing, the study authors created cell models using human skin cells. They then converted these into induced pluripotent stem cells. Then they were able to stimulate these cells to differentiate into different cell types in the inner ear: hair cells, supporting cells, nerve fibers and Schwann cells that isolate neurons. In addition, the researchers were able to take samples of hard-to-reach inner ear tissue from operated patients. The team then showed that Sars-CoV-2 can actually infect the inner ear and, in particular, the hair cells. The scientists also found that the other cell types in their models were not susceptible to corona infection. The results suggest that cochlear hair cells also contain proteins that allow SARS-CoV-2 to enter the inner ear.
Possible ways for the coronavirus to enter the ears include the Eustachian tube that connects the nose to the middle ear. According to the authors of the study, the virus could possibly also escape from the nose through small openings that surround the olfactory nerves. This would allow it to enter the brain space and infect cranial nerves. The researchers now hope to use their human cell models to test possible treatments for the inner ear infections caused by SARS-CoV-2 and other viruses. Although this study strongly suggests that COVID-19 may cause hearing and balance problems, the overall percentage of COVID-19 patients who had ear problems is unknown.