Introduction
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for coronavirus disease 2019 (Covid-19), was first seen in Wuhan, China, in December 2019, and developed into an outbreak worldwide.Reference Huang, Wang, Li, Ren, Zhao and Hu1 Given the rapid emergence of this disease, there are many unknowns about its pathogenetic effects on various organs, and its symptoms, diagnosis and treatment.Reference Huang, Wang, Li, Ren, Zhao and Hu1–Reference Cao3
The most common symptoms of this disease are fever, cough, fatigue and difficulty breathing. In a smaller number of infected people, headache, confusion, gastrointestinal symptoms and nausea have also been reported.Reference Li, Huang, Wang, Wang, Liang and Huang4 Furthermore, anosmia is now associated with Covid-19.Reference Kilic, Kalcioglu, Cag, Tuysuz, Pektas and Caskurlu5 Most patients with Covid-19 show mild to moderate symptoms; however, about 15 per cent develop severe pneumonia, and 5 per cent develop acute respiratory distress syndrome, which eventually leads to shock and multiple organ failure.Reference Huang, Wang, Li, Ren, Zhao and Hu1–Reference Cao3 In addition to causing acute respiratory syndrome, the disease triggers a cytokine storm and activates immune responses. However, uncontrolled inflammatory responses and impaired immune responses can lead to local and systemic tissue damage.Reference Cao3
Research is ongoing into the effects of the virus on other organs in the body. One of these organs is the auditory system. Multiple viral infections can cause sudden sensorineural hearing loss (SNHL). Sudden SNHL is determined as 30 dB or more SNHL occurring in at least three successive frequencies over 72 hours.Reference Kilic, Kalcioglu, Cag, Tuysuz, Pektas and Caskurlu5 A range of aetiological risk factors have been suggested as causes of sudden SNHL, including viral infection, vascular impairment, autoimmune disease, inner-ear pathology and central nervous system anomalies. In most cases, sudden SNHL occurs because of a viral infection.Reference Herman, Vincent, Parietti Winkler, Loundon, Couloigner and Tankere6 Hearing loss caused by these factors can be unilateral or bilateral. This paper reports a sudden SNHL patient who tested positive for Covid-19, and it describes her treatment. We also review previous relevant reports.
Case report
On 12 July 2020, a 60-year-old woman presented to an ENT clinic with sudden hearing loss and subjective tinnitus in her left ear. This patient had a history of previous visits to the clinic and her previous audiometric results showed a mild hearing loss on both sides that could have been age-related (Table 1). Her complaint was unilateral sudden hearing loss in her left ear with severe tinnitus in the same ear that started 2 days earlier. She had no history of ear pain or discharge, dizziness, vertigo, head trauma, ototoxic medications, or upper respiratory tract infection.
Table 1. Pure tone audiometry, speech audiometry and tinnitus loudness in Covid-19 positive patient at each treatment stage
Covid-19 = coronavirus disease 2019; AC/BC = air conduction/bone conduction; HL = hearing loss; SRT = speech recognition threshold; SDS = speech discrimination score; NR = no response
Otological assessment, including otoscopic examination, showed bilaterally normal external auditory canals and opaque tympanic membranes. Tuning fork tests revealed positive Rinne's test results bilaterally, but positive Weber test results were lateralised to the right side.
Audiological assessments, including tympanometry, audiometry and bedside tests were performed. Given the prevalence of SARS-CoV-2, these assessments were performed in full compliance with health protocols. The tympanogram showed type A findings in both ears. Audiometric results showed profound hearing loss in the left ear (Table 1).
Our patient had no symptoms of Covid-19. Although Herman et al. (2020) do not recommend routinely carrying out reverse transcription polymerase chain reaction tests on nasopharyngeal swabs before starting corticosteroid therapy,Reference Herman, Vincent, Parietti Winkler, Loundon, Couloigner and Tankere6 a history of SARS-CoV-2 infection in family members prompted us to request a polymerase chain reaction test for the patient.
Other assessments, such as serological assessment of virus markers and magnetic resonance imaging (MRI) of the brain to rule out abnormalities of the internal auditory meatus, were also requested, to determine the cause of the sudden SNHL.
The next day, after confirmation of Covid-19 on polymerase chain reaction testing, the patient was treated with intra-tympanic injections of corticosteroids (three injections of dexamethasone (24 mg/ml, the preferred unit dose) were provided over a three-week period).Reference Leung, Flaherty, Zhang, Hara, Barber and Burgess7
After the first treatment session, follow-up assessments of pure tone threshold for 0.25–8 kHz, pure tone average (of 0.5, 1 and 2 kHz) and speech audiometry were conducted before each re-injection, as per the treatment protocol. This showed improvement of hearing level and speech perception (Table 1). In addition, the loudness of subjective tinnitus (assessed using numeric rating scales that typically range from 0 or 1 (low loudness) to 10 (high loudness) reduced after treatment, but did not completely disappear (Table 1).
The brain MRI results were normal. In addition, viral serology markers for human immunodeficiency virus, cytomegalovirus, hepatitis B and hepatitis C, and syphilis, were negative. However, C-reactive protein (CRP) levels were increased.
Discussion
We report on a patient referred to us with the only symptom of sudden hearing loss who was diagnosed with Covid-19. The intra-tympanic injection of corticosteroids immediately improved hearing threshold and speech perception, and reduced tinnitus loudness.
Previous studies mention several mechanisms for sudden hearing loss caused by a virus, including: neuritis caused by viral involvement of the cochlear nerve, cochleitis due to viral involvement of the cochlea and peri-lymphatic tissues, and a stress response resulting in the cross-reaction of inner-ear antigens to viral infections.Reference Kilic, Kalcioglu, Cag, Tuysuz, Pektas and Caskurlu5,Reference Harenberg, Jonas and Trecca8 With a mechanism similar to other viruses, Covid-19 can not only increase inflammatory processes in the cochlea and cause a cytokine storm, but also damage the hair cells, Corti organ and stria vascularis.Reference Mustafa9 Our patient did not have the common Covid-19 symptoms, but the polymerase chain reaction test results were positive, and she had increased CRP levels indicating an increase in inflammatory conditions. However, interpretation of the findings should be treated with caution.Reference Degen, Lenarz and Willenborg10 Furthermore, the results of other laboratory tests, such as virus tests and imaging, were normal, raising our suspicions of SARS-CoV-2 infection as the cause of sudden SNHL.
Despite the low numbers of studies, it is important to consider the possibility of a relationship between Covid-19 and sudden SNHL. So far, five papers (described below) that report sudden SNHL in a SARS-CoV-2 polymerase chain reaction positive patient have been published. In some of the patients, sudden SNHL was secondary to Covid-19 disease (post Covid-19) and was accompanied by other symptoms; in other patients, sudden SNHL was the only symptom of Covid-19 disease.
Kilic et al., in June 2020, reported that one out of five Covid-19 patients had sudden SNHL and no other common symptoms of Covid-19.Reference Kilic, Kalcioglu, Cag, Tuysuz, Pektas and Caskurlu5 For management of this patient, they used only oral hydroxychloroquine to control Covid-19. Although no common corticosteroid injections were considered, the patient reported hearing improvement after treatment. They focused on treating Covid-19 in order to avoid the detrimental effects of using conventional methods of treating sudden hearing loss with steroids,Reference Kilic, Kalcioglu, Cag, Tuysuz, Pektas and Caskurlu5 although the use of hydroxychloroquine itself can lead to cochlear damage.Reference Prayuenyong, Kasbekar and Baguley11 However, their study did not include imaging or laboratory evaluations to rule out other possible causes of sudden SNHL.Reference Kilic, Kalcioglu, Cag, Tuysuz, Pektas and Caskurlu5
Karimi-Galougahi et al., in June 2020, reported three polymerase chain reaction Covid-19 positive patients who presented with SNHL.Reference Karimi-Galougahi, Naeini, Raad, Mikaniki and Ghorbani12 Their article did not publish detailed information about other assessments or treatments, and only once mentioned the possible relationship between Covid-19 and hearing loss.Reference Karimi-Galougahi, Naeini, Raad, Mikaniki and Ghorbani12
In July 2020, Abdel Rhman and Abdel Wahid reported a patient with unilateral sudden SNHL with a positive Covid-19 polymerase chain reaction test result who did not have the common Covid-19 symptoms.Reference Abdel Rhman and Abdel Wahid13 They used intra-tympanic corticosteroid injection (methylprednisolone), which was effective in improving hearing.
In September 2020, Lang et al. reported a patient with common Covid-19 symptoms who developed unilateral sudden hearing loss after symptom offset.Reference Lang, Hintze and Conlon14 Three weeks after the hearing loss onset, oral prednisolone was administered to the patient. Unfortunately, as expected, there was no improvement in the patient's hearing because of the delay in treatment.Reference Lang, Hintze and Conlon14
Koumpa et al., in October 2020, described a man in the UK who developed sudden-onset hearing loss a week after transfer out of the intensive care unit following Covid-19.Reference Koumpa, Forde and Manjaly15 They applied oral prednisolone for one week, which resulted in partial subjective improvement in his hearing. They then used intra-tympanic steroid injection (methylprednisolone), which resulted in no further hearing improvement as observed on pure tone audiograms.Reference Koumpa, Forde and Manjaly15
These studies highlight the use of corticosteroids in patients with Covid-19. Nevertheless, it is believed that corticosteroid use delays viral RNA clearance; furthermore, corticosteroids have serious side effects.Reference Russell, Millar and Baillie16 However, Mahase (2020) reported that applying a low dose of steroids may reduce the mortality rate in ventilated patients with Covid-19 by up to one-third, but have no effect on patients with mild Covid-19.Reference Mahase17
Given the conflicting findings regarding the side effects of corticosteroids in Covid-19 patients, the patient in the current case study was treated with intra-tympanic steroid injections. The use of intra-tympanic steroids resulted in higher perilymph steroid levels; it increased chances of recovery (compared with systemic administration) but involved minimal systemic absorption.Reference Koumpa, Forde and Manjaly15 The advantages of using corticosteroids are well established, as is the likely superiority of intra-tympanic injections compared to systemic administration.Reference Herman, Vincent, Parietti Winkler, Loundon, Couloigner and Tankere6 Therefore, it is suggested that in the current situation, in patients with coronavirus, use of intra-tympanic injections may have a minimal risk.
Regarding corticosteroids, we used dexamethasone. In comparison to prednisone and dexamethasone, research shows that dexamethasone has a higher biological half-life and greater anti-inflammatory properties than prednisone. The increased anti-inflammatory properties of dexamethasone may provide advantages for viral and autoimmune aetiologies of sudden SNHL.Reference Leung, Flaherty, Zhang, Hara, Barber and Burgess7
• Few studies have reported sudden sensorineural hearing loss (SNHL) as a possible symptom of coronavirus disease 2019 (Covid-19)
• In some patients, sudden SNHL was secondary to Covid-19 (post Covid-19) and was accompanied by other symptoms; in others, sudden SNHL was the only symptom
• In our Covid-19 positive, sudden SNHL patient, hearing threshold and speech perception improved, and tinnitus loudness decreased after intra-tympanic corticosteroid injection
• Coronavirus may be a cause of sudden SNHL
• The hearing status of Covid-19 patients and incidence of Covid-19 in sudden SNHL patients should be considered
• Patients presenting with sudden SNHL who are positive or suspected for Covid-19 should receive intra-tympanic corticosteroid injection
Another point to consider in patients with sudden SNHL is the timing of steroid injection therapy. The sooner the therapeutic intervention is commenced, the better the chances of recovery and the fewer destructive effects on the cochlea.Reference Herman, Vincent, Parietti Winkler, Loundon, Couloigner and Tankere6 In the current reported patient, because of their Covid-19 positive status, treatment with intra-tympanic corticosteroid injection was performed within 72 hours of symptom onset.
Conclusion
This case report supports previous evidence from other case reports and small case series suggesting a possible association between Covid-19 and sudden SNHL. Coronavirus should perhaps be added to the list of known viruses that can lead to sudden SNHL. We recommend that patients who present with sudden SNHL and who are positive for Covid-19 undergo injection therapy immediately. In addition, asking about the hearing status of those with Covid-19 could prompt immediate effective therapeutic action; likewise, determining Covid-19 status or history in cases of sudden hearing loss could help to break the chain of virus transmission, especially in those who have been in close contact with a confirmed or probable case of Covid-19.
Acknowledgement
Thanks to Mr Mohsen Ershad for his help with this article.
Competing interests
None declared
