Some viral infections, such as mumps, measles, and meningitis, can cause hearing problems. In the current coronavirus disease 2019 (COVID-19) pandemic, reports of audio-vestibular symptoms have emerged.
Researchers at the University of Manchester, UK, aimed to systematically review the literature to provide evidence on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and audio-vestibular symptoms. They found that COVID-19 has been tied to hearing loss, vertigo, and tinnitus.
The study, published in the journal International Journal of Audiology, showed that 7 to 15 percent of adults diagnosed with COVID-19 report audio-vestibular symptoms. The most common symptom is tinnitus or ringing in the ears, followed by hearing loss and vertigo.
The COVID-19 pandemic, caused by SARS-CoV-2, first emerged in Wuhan City, China, in December 2019.
Early in the pandemic, there was limited information on the potential complications tied to the infection. Most COVID-19 cases are mild or asymptomatic, while others develop into severe illness.
It is well known that some viral infections may cause hearing loss, including measles, rubella, and cytomegalovirus.
Meanwhile, COVID-19 has been linked to some neurological manifestations, like Guillain Barre Syndrome, which has also been found to cause auditory neuropathy spectrum disorder.
In the current study, the researchers aimed to conduct a systematic review of coronavirus and audio-vestibular symptoms.
To arrive at the study findings, the team searched studies about COVID-19 and audio-vestibular symptoms. They found seven studies reporting hearing difficulties, tinnitus, and vertigo tied to COVID-19.
The most common condition is tinnitus, affecting about 17 percent of all adults. Most individuals who reported tinnitus also have hearing loss, hinting at a close link between the two conditions.
Tinnitus was investigated and identified in 15 cross-sectional studies. Of these, three asked the participants to classify their tinnitus to be intermittent or continuous. A participant described the tinnitus as non-pulsatile, while another one said it was akin to white noise.
In COVID-19, the reason why tinnitus occurs in infected people is unclear. The researchers said a potential reason could be that the virus attacks and damages the auditory system. Also, the mental and emotional stress brought by the pandemic may be a trigger.
Hearing problems linked to COVID-19 have been reported across a wide age range and disease severity. There were reports of sudden hearing loss in one ear, often accompanied by tinnitus.
Yet, while the number of COVID-19 cases globally has increased dramatically, it is difficult to determine if the cases of sudden hearing loss are higher than what was reported each year.
About 17 case reports and one case series reported hearing difficulty as a potential COVID-19-related symptom. Of these reports, nine showed a sensorineural hearing loss, three reported conductive hearing loss, and one demonstrated mixed hearing loss. The others did not provide sufficient details to identify the type or severity of the hearing loss.
Another common symptom of COVID-19 reported by patients is dizziness. It is hard to differentiate this from rotary vertigo, which hints at the damage to the balance system of the inner ear.
Among the reviewed studies, nine case reports mentioned rotary vertigo, a common symptom of vestibular dysfunction. Also, the vestibular function tests and the diagnosis, including vestibular neuritis, were reported in four studies.
Other ear-related symptoms were reported, including otalgia, otitis media, changes to the ear canal, ear congestion, and ear fullness. Meanwhile, three studies reported two more ear-related symptoms, such as hyperacusis and phonophobia, which are hypersensitivity and overwhelming fear of sounds, respectively.
The team noted that though there is increased quality and quantity of studies investigating the link between audio-vestibular symptoms and COVID-19, these were all based on case reports and surveys, which rely on self-reports.
There is a need for studies reporting a comprehensive assessment of audio-vestibular function in COVID-19 patients, compared with matched controls.