A new study by researchers from the Massachusetts Institute of Technology (MIT) and Massachusetts Eye and Ear showed that SARS-CoV-2, the virus that causes COVID-19, could infect tissues in the inner ear that is important for balance and hearing.
Researchers said that the virus could infect the eardrum and the Schwann and hair cells, which may lead to hearing loss, The NU Herald reported.
More Evidence Links COVID-19 to Hearing Loss
Previous studies have shown that some COVID-19 patients have complained of ear issues, like auditory impairment and tinnitus. Some have also complained of lightheadedness and issues in their balance, which suggests that SARS-CoV-2 may have affected their inner ear.
In the study, titled "Direct SARS-CoV-2 Infection of the Human Inner Ear May Underlie COVID-19-associated Audiovestibular Dysfunction," published in the journal Communications Medicine, researchers analyzed cellular models of the inner ear of an adult human with SARS-CoV-2.
Lee Gehrke, who co-led the study, said that these models are the first step in working not only in SARS-CoV-2 but also other viruses that damage hearing.
According to Yahoo! News, researchers used the hard-to-get adult human inner ear tissue for their models and found that both human and mouse inner ear cells allow entry of the SARS-CoV-2 virus through the eustachian tube that connects the nose to the middle ear or through the small openings that surround the olfactory nerves.
Konstantina Stankovic, a co-led of the study, told MIT News that the virus could enter the brain and infect cranial nerves that connect to the inner ear. Also, it infects Schwan and hair cells that are responsible for hearing.
COVID-19 Worsens Problems in Hearing and Balance
The researchers wrote in their study that their findings suggest that COVID-19 may worsen inner ear infections associated with problems in hearing and balance. But the overall percentage of COVID-related ear problems remains unknown until today.
Stankovic said that these cases were initially not detected due to a lack of readily available routine testing on COVID-19 patients. But those suffering from the severe form of the infection were also not paying much attention to whether their hearing was reduced or whether they were already suffering tinnitus.
"We still don't know what the incidence is, but our findings really call for increased attention to audiovestibular symptoms in people with [COVID-19] exposure," Yahoo! News quoted Stankovic.
The researchers hope to use their human inner cell models to test potential treatments for COVID-related inner ear infections as well as other viruses.
Schwann and Hair Cells
Emergency physician Dr. Robert Glatter of Lenox Hill Hospital in New York told Healthline that vestibular hair cells serve as sensory receptors in the inner ear that assess and monitor head motion that gives a sense of balance on animals and humans.
Meanwhile, the second type of cell found in the inner ear called the Schwann cells plays a vital role in hearing. Glatter said that the study showed the crucial roles that these cells play when the SARS-CoV-2 virus enters the inner cell.
These cells, along with the ACE2 receptor and enzymes furin and transmembrane protease serine 2, allow the virus to attach to the host cell, infecting the inner ear.
RELATED ARTICLE: Researchers Assess Pre-Existing or Developed Tinnitus During the Pandemic
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