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The more you learn about COVID-19 the more there is to dislike about it. The global death toll from the virus is now more than five million and for those who survive there can be long-term health consequences. We know COVID can attack the lungs, heart and brain. Now we are learning it can also mess up your ears causing hearing problems, ringing in the ear (tinnitus) and leave you dizzy.
Viral infections are a known cause of hearing loss and other kinds of infection. That’s why, before the pandemic started, Dr. Konstantina Stantovic at Massachusetts Eye and Ear and Dr. Lee Gherke at MIT had been studying how and why things like measles, mumps and hepatitis affected people’s hearing. After COVID hit they heard reports of patients experiencing sudden hearing loss and other problems, so they decided to take a closer look.
They took cells from ten patients who had all experienced some hearing or ear-related problems after testing positive for COVID and, using the iPSC method, turned those cells into the kind found in the inner ear including hair cells, supporting cells, nerve fibers, and Schwann cells.
They then compared those to cells from patients who had similar hearing issues but who had not been infected with COVID. They found that the hair and Schwann cells both had proteins the virus can use to infect cells. That’s important because hair cells help with balance and the Schwann cells play a protective role for neuronal axons, which help different nerve cells in the brain communicate with each other.
In contrast, some of the other cells in the inner ear didn’t have those proteins and so were protected from COVID.
In a news release Dr. Stankovic says it’s not known how many people infected with COVID experienced hearing issues. “Initially this was because routine testing was not readily available for patients who were diagnosed with COVID, and also, when patients were having more life-threatening complications, they weren’t paying much attention to whether their hearing was reduced or whether they had tinnitus. We still don’t know what the incidence is, but our findings really call for increased attention to audio vestibular symptoms in people with Covid exposure.”
The doctors are not sure how the virus gets into the inner ear but speculate that it may enter through the Eustachian tube, that’s a small passageway that connects your throat to your middle ear. When you sneeze, swallow, or yawn, your Eustachian tubes open, preventing air pressure and fluid from building up inside your ear. They think that might allow particles from the nose to spread to the ear.
The study is published in the journal Communications Medicine.
CIRM has funded 17 different projects targeting COVID-19, several of which are still active.