Research recently carried out at the Massachusetts Institute of Technology and Massachusetts Eye and Ear showed that Covid-19 can be transmitted via the inner ear, which contains important hair cells. We rely on these hair cells for both hearing and balance. Ten COVID patients who reported inner ear problems were used in the study, which was published in MIT News.
The study was only possible because of the cutting edge work carried out by the researchers, according to the report. Researchers created a new cell model of the inner ear, which enabled them to discover the difficult to pinpoint inner ear issues. They couldn’t do this before because adult inner ear tissue is hard to find. Because of this, studies on viruses that cause deafness have come up against a scientific brick wall.
Although the study has come as a breakthrough for COVID-linked deafness and related issues, it began before the pandemic. At the beginning of last year, study lead Lee Gehrke and second lead Konstantina Stankovic began their joint project at Massachusetts Eye and Ear, according to the report. The goal was to develop a cellular model for studying inner ear infections in humans.
The ultimate purpose was to find possible answers to defeating viral deafness-causing infections, such as hepatitis, cytomegalovirus, and mumps. The planned project’s outcome altered as the pandemic took hold. Patients began reporting symptoms of deafness, tinnitus, and dizziness. As patients experiencing hearing loss symptoms began testing positive for COVID, there was no obvious correlation because of how common their symptoms were. At this point, researchers decided to focus on using their cellular model to study the SARS-CoV-2 infection.
“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,” Gehrke said.
“This work opens a path now for working with not only SARS-CoV-2, but also other viruses that affect hearing.”
According to the study, possible routes for the virus to enter the ears include the Eustachian tube, which connects the nose to the middle ear. “The virus may also be able to escape from the nose through small openings surrounding the olfactory nerves,” Stankovic told MIT News. “That would allow it to enter the brain space and infect cranial nerves, including the one that connects to the inner ear.”
In the 10-patient study, nine experienced tinnitus. Six reported dizziness. All were found to have mild to severe hearing loss and were post positive COVID-19 infection. When otoacoustic emission testing (auditory stimuli used to measure damage to cochlear hair cells) was carried out, all the subjects had negative results in varying degrees.
This study highlights that Covid-19 can and does cause infection and subsequent hearing loss and inner ear infections in at least an apparent majority of people infected. It is currently unknown just how widespread this could be. Further testing on a much larger scale is needed,
however, this is an important step forward in understanding COVID-19’s links to inner ear deafness, dizziness, and tinnitus.