COVID-19 can infect the inner ear and potentially trigger a host of auditory problems, a new small study suggests.
Researchers at the Massachusetts Institute of Technology (MIT) and Massachusetts Eye and Ear looked at 10 Covid patients who reported a number of ear-related symptoms.
They found that the virus can infect inner ear cells, specifically hair cells, which may lead to hearing and balance problems.
The team says the findings explain why some COVID-19 patients have reported hearing loss, tinnitus, dizziness and difficulties with balance.
A new study found inner ear cells have proteins the coronavirus needs in order enter and infect cells, which may explain why some COVID-19 patients have reported hearing loss, tinnitus, dizziness and difficulties with balance (file image)
Co-lead authors Dr Konstantina Stantovic and Dr Lee Gherke had been studying why viruses such as mumps and hepatitis affect hearing before the pandemic struck.
In March 2020, after they began to see coronavirus patients report deafness, dizziness or tinnitus, they decided to focus on Covid.
‘It was very unclear at the time whether this was causally related or coincidental, because hearing loss and tinnitus are so common,’ Stantovic, former chief of otology and neurotology at Massachusetts Eye and Ear and current chair of the Department of Otolaryngology-Head and Neck Surgery at Stanford University School of Medicine, said in a statement.
For the study, published in the journal Communications Medicine, the team used new cellular models of human inner ear cells and hard to obtain human inner ear.
Other studies have been hampered by a lack of inner ear tissue, they claim.
‘Having the models is the first step, and this work opens a path now for working with not only SARS-CoV-2 but also other viruses that affect hearing,’ said Gehrke, a professor in MIT’s Institute for Medical Engineering and Science, in a statement.
They took human stem cells and changed them into ‘pluripotent’ stem cells, which can take on many different forms in the body.
Researchers changed the stems cells into different types of inner ear cells including hair cells, supporting cells, nerve fibers and Schwann cells, which could be grown in a 2D layer or 3D organoids.
Cells were then taken from the 10 Covid patients undergoing surgery for a condition which causes vertigo attacks or a tumor that causes severe hearing loss and dizziness.
In both the models and the human ear samples, the team found hair cells and Schwann cells had proteins the coronavirus needs to have in order enter and infect cells.
This is especially important because hair cells help people keep balance and understand their head motion.
The virus could not enter the other cell types they studied.
It’s not understood how the virus gets into the inner ear, but it may enter through a tube connecting the nose to the middle ear or escape from the nose.
Another theory is that it escapes from the nose through small openings surrounding the olfactory nerves, and infects cranial nerves, including the one that connects to the inner ear.
Researchers don’t know the percentage of virus patients report hearing difficulties, a problem made worse by a lack of testing early in the pandemic.
‘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,’ Stankovic said.
‘We still don’t know what the incidence is, but our findings really call for increased attention to audiovestibular symptoms in people with Covid exposure.’