Is There a Causative Link Between SARS-CoV-2 and Audiovestibular Dysfunction?

What elements characterize the causal relationship between SARS-CoV-2 and audiovestibular symptoms?

BOTTOM LINE

SARS-CoV-2 can infect human inner ear cell types, and this infection may underlie COVID-19–associated problems with hearing and balance.

BACKGROUND: Caused by SARS-CoV-2 virus, COVID-19 has been associated with various sensory deficits. However, reports of audiovestibular symptoms in COVID-19 patients often rely on self-reporting and lack documentation. Although coronaviruses are a common cause of middle ear infection, their role in inner ear infection has not been systematically studied.

COMMENT: This is an amazing article from a division of Nature. The authors say it best: “We also generated some of the first human cellular models of infectious inner ear disease. We show that human and mouse inner ear cells have the molecular machinery to allow SARS-CoV-2 entry. We further show that SARS-CoV-2 can infect specific human inner ear cell types. Our findings suggest that inner ear infection may underlie COVID-19-associated problems with hearing and balance.” —Sujana Chandrasekhar, MD

STUDY DESIGN: Prospective cohort study/animal study.

SETTING: Department of Otolaryngology–Head and Neck Surgery, Harvard Medical School, Boston, Mass.

SYNOPSIS: Researchers examined human inner ear tissue of 10 COVID-19 patients with audiovestibular symptoms, in vitro 2D and 3D cellular models of the human inner ear, and mouse inner ear tissue. Nine of the 10 patients had experienced common COVID-19 symptoms between 21 days before and 14 days after onset of hearing loss, tinnitus, or vertigo. Authors noted that the temporal relationship between audiovestibular symptom onset in the patients and positive COVID-19 testing implicates SARS-CoV-2 infection as the cause. None of the patients had evidence of middle ear infection, while all exhibited sensorineural hearing loss. Results of human tissue testing demonstrated that vestibular hair cells and Schwann cells are potential targets of SARS-CoV-2 in human peripheral vestibular organs. Data from examination of the models confirmed that SARS-CoV-2 proteins are produced during virus replication, and data from mouse tissue examination demonstrated that SARS-CoV-2 entry-related genes are expressed in the mouse inner ear. Authors state that findings suggest several possible mechanisms for audiovestibular symptoms in COVID-19 patients. Study limitations included its small size and the lack of universal testing results as reference.

CITATION: Jeong M, Ocwieja KE, Han D, et al. Direct SARS-CoV-2 infection of the human inner ear may underlie COVID- 19–associated audiovestibular dysfunction. Comm Med (Lond). 2021;1:44.