WASHINGTON - Sensory symptoms, including loss of taste and smell, sometimes come with COVID-19, but a new study found that COVID-19 can also infect inner ear cells, causing hearing and balance issues in some COVID-19 patients.
In the study, published Oct. 29, researchers at MIT and Massachusetts Eye and Ear examined hearing and balance symptoms in patients with COVID-19. The team also studied inner ear tissue and cells in humans and mice to determine the virus’s effect.
Ten adult patients who developed audiovestibular dysfunction within three weeks of COVID-19 diagnosis, confirmed by PCR or serum antibody testing, were studied. The hearing loss ranged from mild to profound.
CT Scan of Inner Ear (Photo by: BSIP/Universal Images Group via Getty Images)
The results, which appeared in the journals from the National Institutes of Health and "Communications Medicine," found nine of the 10 patients experienced tinnitus — a ringing or buzzing noise in one or both ears. And six patients experienced vertigo — a sudden spinning sensation.
"The timing of symptom onset suggested a correlation between COVID-19 infection and hearing loss," Dr. Brian Doctrow, Ph.D. with the National Institutes of Health, wrote.
The researchers found infection by COVID-19 requires certain proteins on the host cell surface. They found these proteins on two types of inner ear cells — hair cells and Schwann cells.
The team also developed models of inner ear tissue that they could use for further investigation. They took cells from human skin that were reprogrammed to become stem cells. They then directed the stem cells to develop into precursors of either hair cells or Schwann cells.
Like the human inner ear samples, these cells had the proteins needed for infection. COVID-19 infected the hair cell precursors and, to a lesser extent, the Schwann cell precursors.
"The virus was able to infect the hair cell-like cells in the organoids," the NIH wrote. "Together, these results point to SARS-CoV-2 infection of the inner ear as a cause of COVID-19-associated hearing and balance issues."
While other senses like taste and smell have been more widely studied and reported, hearing and balance symptoms associated with COVID-19 have not been as thoroughly studied.
Still, the overall percentage of COVID-19 patients with ear-related issues is unknown.
"This work opens a path now for working with not only SARS-CoV-2 but also other viruses that affect hearing," Dr. Lee Gehrke, a lead researcher of the study, noted.
Another lead researcher, Konstantina Stankovic, told FOX News that the team now hopes to use their human cellular models to test possible treatments for the inner-ear infections caused by COVID-19 and other viruses.
This story was reported from Los Angeles. FOX News contributed.