Current research in otolaryngology focuses on the optimal route of steroid delivery for treating sensorineural hearing loss. To date, however, SSNHL in the context of COVID-19 has been extensively recognized, since COVID-19 has been identified in a number of recent case reports as the cause of SSNHL [15,16,17,18].
Despite the many symptoms linked with the SARS-CoV-2 virus, the relationship between COVID-19 and hearing has received little attention. Mustafa (2020) examined the transient-evoked optoacoustic emissions (TEOAE) of twenty SARS-CoV-2-positive patients and found that their pure high-frequency tone audiometry thresholds and TEOAE amplitudes were considerably lower than those of healthy individuals. This suggests that COVID-19 might be associated with cochlear injury [19].
The loss of hair cells and supporting cells of the organ of Corti in the cochlea of SSNHL patients in the absence of inflammatory cell infiltration suggests that the pathophysiology of idiopathic SSNHL may involve cellular stress pathways [20]. With ACE-2 receptors, alveolar epithelial cells and pulmonary endothelium cells are sensitive to SARS-CoV-2 infection. Moreover, SARS-CoV-2 generates an inflammatory response and an increase in cytokines, such as tumor necrosis factor-α, interleukin-1, and interleukin-6 [21].
Another theory is that COVID-19 causes microvascular changes (thrombus or embolus) that result in ischemic injury to the inner ear or auditory centers [22]. Multiple outcomes, including arterial and venous thrombosis and multiorgan failure, have been linked to COVID-19 infection. This might be due to endothelins, which can damage the auditory center of the temporal lobe, the cochlear nerve, and/or cochlear tissues [23].
Kılıç et al. discovered that one in five patients with SSNHL had a positive COVID-19 PCR screening test, showing that COVID-19 and SSNHL are linked and that COVID-19 may increase the prevalence of SSNHL. They found that SSNHL might be an asymptomatic sign of COVID-19 or the only symptom. Knowledge of such a generic COVID-19 presentation is essential for preventing the spread of infection during the current pandemic by isolation and early delivery of COVID-19-specific medication. After administering 200 mg of oral hydroxychloroquine twice daily for 5 days, the COVID-19-positive patient in this study was completely cured with SSNHL [24].
Beckers et al. revealed significant evidence between COVID-19 with hearing loss. They proposed adding PCR testing into the diagnostic assessment of SSNHL patients during the present epidemic. According to the researchers, SSNHL may be caused by micro-thrombosis in endothelial cells of the cochlear or central auditory pathway [25].
Fidan et al. noticed an increase in the frequency of SSNHL during COVID-19. In addition, 39 of 68 SSNHL patients have positive nasopharyngeal swabs for SARS-CoV-2 (57.4%). In addition, they discovered that the neuroinvasion and autoimmune models describe COVID-19 and cranial neuropathy the best [26].
Despite this, Chari et al. found that the incidence of SSNHL did not vary between March and May during the pandemic and was also the same as the previous year, demonstrating that the COVID-19 virus does not increase the incidence of SSNHL [27]. In addition, Aslan and içek found that the incidence of SSNHL did not statistically change between the 1-year period before and after the pandemic. They offered two justifications for this. First, the pandemic may have suspended healthcare services for patients. The number of patients with SSNHL caused by a virus may have decreased as a result of current limitations and preventative measures [28].
In the current study, the onset of hearing loss post-COVID infection ranged from 1 to 3 months with a median (IQR) of 2.0 (1.5–2.5) months which is a delayed onset complaint. Beckers et al. observed that SSNHL may manifest during the terminal phase of disease since many patients did not recognize their hearing loss until they were discharged from the hospital or critical care unit [29].
Fidan et al. studied the difference between 2019 and 2020 years regarding the duration of SSNHL and asked for medical acclaim. They found that this duration was longer in the 2020 group than in the 2019 group (median = 2.3 days vs. 0.6 days, respectively) (P < 0.001) [26].
Koumpa et al. observed unilateral sudden hearing loss in an ICU patient being monitored for COVID-19, despite the patient’s assertion that hearing loss was not among his or her symptoms upon hospital admission [30].
Even though oral corticosteroids are often used for SSNHL, the evidence of their effectiveness is still equivocal. The physician may prescribe oral corticosteroids as first-line therapy for the patient in compliance with AAO-HNS criteria, notwithstanding the scarcity of evidence supporting their efficacy [31].
Corticosteroids used to treat influenza and other viruses may delay viral RNA clearance but do not reduce mortality, according to Russell et al. They advised against taking corticosteroids in such a situation [32]. In contrast, according to studies conducted at the University of Oxford by Mahase, steroids lowered mortality in ventilated patients and/or those receiving oxygen assistance but had no effect on mortality in those who did not need oxygen support. Bell’s palsy and SSNHL cannot be considered distinct symptoms/signs of COVID-19; hence, effective corticosteroids will be administered to these people [33].
The steroid dose and the effect of starting therapy at different times are also debatable. Westerlaken et al. compared the efficacy of pulse therapy of 300 mg intravenous (IV) methylprednisolone to that of standard oral prednisolone therapy for SSNHL [34]. Eftekharian and Amizadeh found similar results in their study [35]. In addition, the German Association of Scientific Medical Societies (AWMF) advocated high-dose intravenous steroid treatment (250 mg) [36].
However, Alexiou et al. and Egli Gallo et al. have shown that high-dose systemic steroid therapy is superior to conventional systemic corticosteroid therapy [37].
Several variables influence the possibility of SSNHL recovery. Age is recognized as the most constant factor with a negative effect since the recovery rate for senior patients is much lower [38,39,40]. This is in line with the findings of the present investigation, which revealed a negative association between recovery and age.
In this investigation, there was no correlation between the presence of tinnitus or vertigo and the improvement of SSNHL. Except that, vertigo was frequent in severe instances (those with a lower PTA threshold), and tinnitus was common even in moderate ones. Several studies indicate that vertigo is connected with a bad outcome [11, 38]. This outcome has not, however, been constant [39, 40]. Multiple studies have shown that tinnitus is a positive [41], negative [11], and neutral [42] prognostic indicator.
Those who contact a physician within a week have a greater chance of recovering from hearing loss than those who wait longer [38,39,40]. This is similar to the results of the current study, which revealed a negative correlation between recovery and the duration of SSNHL development after COVID-19 infection.
Patients with severe hearing loss were less likely to recover than those with moderate hearing loss [38, 43].
In this investigation, there was no correlation between hearing recovery and hearing loss configuration. Chang et al. and Huy and Sauvageau investigated the configuration of hearing loss in individuals with moderate to severe hearing loss. They discovered that hearing recovery was decreased with a flat audiogram. For non-flat settings, an ascending audiogram exhibited a more favorable prognosis than a descending audiogram [11].
We found no correlation between hearing recovery and broad systemic disorders in our investigation. In some investigations, systemic comorbidities such as diabetes mellitus, hyperlipidemia, and/or hypertension were associated with a worse result [43].
Regarding the timing of treatment in relation to the development of symptoms, it has been traditional to start steroid medication as soon as possible (within the first 2 weeks). The Mann-Whitney and Fisher exact tests demonstrated a high connection between hearing improvement, and the date corticosteroid therapy was started in the current study. Numerous studies demonstrate that the length of time between the onset of symptoms and the initiation of therapy is detrimental to prognosis [38]. The recovery rates of patients who sought medical counsel and began treatment during the first week of sickness onset, within 2 weeks and 3 months later, were 87%, 52%, and 10%, respectively [39, 40, 44]. The AAO-HNS suggests beginning steroid treatment within 2 weeks [31].
