Introduction

SARS-CoV-2 virus can infect a wide range of cells and systems of the body [1]. Coronavirus could damage the hearing by several mechanism, it could damage the auditory center in the temporal lobe, as a viral infection mediated consequence or could change the microvascular structure & functions of the inner ear, resulting in a thrombus or an embolus that interrupts the blood flow to the inner ear, or there could be any multi-organ involvement and can occur as a direct peripheral injury to the sensory cells of the cochlear due to neurotropism of the virus [2]. The aim of this study is to evaluate irreversible hearing loss and other associated otorhinolaryngology symptoms, Assess the audiological profile and association of hearing loss with severity of covid-19 disease in post covid-19 patients.

Material and Method

A prospective hospital-based observational study was carried out in the department of ear, nose, and throat (ENT) of a tertiary care medical college and associated hospital during a period of 22 months from January 2021 to October 2022. A total of 100 Post Covid-19 patients were selected from the outpatient department of ENT, Medicine, TB & Chest and Anaesthesia fulfilling the inclusion criteria (patients between 18 and 50 years of age and patients with history of covid infection within 4–6 weeks duration) and exclusion criteria (cases with Chronic Suppurative Otitis Media, Presbycusis, Acoustic trauma, Meniere’s disease, autoimmune disease occupational exposure or ototoxicity and with other co-morbidities like HTN, DM). After taking proper written informed consent and institutional ethical clearance. Complete history was taken to categorise the patients according to severity of covid-19 infection. Audiological assessment was done at 1st visit of all patients. Those patients who were found to have hearing loss were followed up to 6 months, with pure tone audiogram done at interval of 1 month, 3 months and 6 months to assess the irreversibility of hearing loss. Relevant data were collected and statistically analysed using the Chi-squared test.

Results

In our study, 100 Post covid-19 patients were selected on the basis of history and previous RT-PCR reports and asses the audiological profile of symptomatic patients were assessed, along with association of severity of covid-19 infection.

Male patients were more common, out of 100, 72 (72%) were male and 28 (28%) were female with male to female ratio 2.5:1. Mean age of patients was 42.06 years. (Table 1) Majority of the patients (66%) belong to the 5th decade, 28(28%) patients were in age group 31–40 years, 5 (5%) patients belonged in 20–30 years category, and only 1(1%) patient was in the age group 18–20 years (Table 2). There were more patients belonging to rural area (56%) than urban (44%) (Table 3). Out of 100 patients, 38 (38%) had history of mild severity of infection of Covid-19 while 40(40%) belonged to moderate severity whereas 22 (22%) were having history of severe Covid-19 infection (Table 4). Among those 100, 33 patients develop symptoms in which majority of them develops between 2nd and 3rd week (Table 5). Otorhinolaryngology related symptoms were seen 38 patients, out of 38, majority of them had history of moderate (37.5%) and severe (59%) covid-19 infection with (13.1%) patients with mild covid infection (Table 6). Aural fullness was the presenting complain of 25% patients followed by Hearing loss (20%), (9%) were suffering from tinnitus, (3%) were having episodes of vertigo (Table 7). Among patients having hearing loss, 7(35%) were suffering from unilateral hearing loss in which 5 (25%) patients had their right ear affected whereas in 2(10%) had left ear was diseased and 13 (65%) were suffering from bilateral hearing loss. (Table 8). Audiological assessment was done, twenty post covid-19 patients were having documented hearing loss out of which 15 (15%) were having conductive hearing loss, sensorineural hearing loss was seen in 3(3%) and 2 (2%) were found to have mixed hearing loss (Table 9). Out of 20, 11 were having mild conductive hearing loss, 4 were having moderate conductive hearing loss, moderate SNHL was seen in 2 patients whereas Severe SNHL, moderate mixed hearing loss and moderately severe mixed hearing loss had equal distribution 1 patient each (Table 10). Out of 15 Condutive hearing loss patients, 4 patients have retracted tympanic membrane and 4 patients have C type curve in Tympanometry. Tables 11 and 12 Follow up by repeat audiological profile (PTA) was done after an interval of 1 month, 13 patients were found to have normal hearing, 2 patients were having conductive hearing loss, 3 were having SNHL and 2 were having mixed. Repeat PTA was done after 3 months, 18 patients found to have normal hearing, remaining 2 patients, 1 patient was having mixed hearing loss and other one SNHL, these patients followed up till 6 months and again PTA was done where only 1 patient continue to have sensorineural hearing loss (Table 13).

Table 1 Gender distribution among 100 Post Covid-19 patients
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Table 2 Age-wise distribution among 100 Post covid-19 patients
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Table 3 Geographical distribution among 100 Post Covid-19 patients
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Table 4 Showing the severity of COVID-19 according to WHO among 100 Post covid-19 patients
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Table 5 Time to onset of symptoms in Post covid-19 patients
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Table 6 Showing the comparison between severity of COVID-19 and symptomatology
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Table 7 Symptomatology among 100 Post covid-19 patients
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Table 8 Showing distribution of laterality of hearing loss
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Table 9 Showing hearing loss in post Covid-19 patients
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Table 10 Showing the degree of hearing loss in Post covid-19 patients according to WHO criteria
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Table 11 Showing otoscopic findings in patients with CONDUCTIVE hearing loss (CHL)
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Table 12 Showing tympanometry findings in patients with CHL
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Table 13 Showing the Audiological profile of patients after 1, 3 and 6 months of follow up by pure tone audiogram (PTA)
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Discussion

Sudden onset sensorineural hearing loss (SSNHL) is defined as a hearing loss of at least 30 dB in at least three consecutive frequencies that has developed within 3 days [3]. Viruses causing hearing loss have been described, mainly including the herpes species and cytomegalovirus, but these are uncommonly seen as the cause of SSNHL [4].

Sensorineural hearing loss (SNHL), tinnitus, and/or vertigo have been described to occur during and following COVID-19 infection. The high rate of chemosensory impairment in COVID-19 patients endorses the neuro-invasiveness features of SARS-CoV-2. Proposed mechanisms of injury encompass direct damage to the labyrinth or cochlear nerve, reactivation of latent virus within spiral ganglion and immune-mediated mechanism in systemic viral infection. Typically, virus-induced hearing loss is sensorineural in nature ranging from mild to profound and either unilateral or bilateral [5]. Chern et al. attributed intra-labyrinthine haemorrhage secondary to COVID-19 associated coagulopathy as a mechanism of hearing loss [6]. the first case of hearing loss in a COVID-19 positive patient was reported on March 15, 2020, from Thailand.

In present study, we included 100 Post covid-19 patients, out of 100 patients, 72 were male and 28 were female. Males were more common than females with male to female ratio 2.5:1. Xiangming Meng et al. [7]. accounted a female preponderance in their systematic review which included 23 patients, out of 23, 11 males and 12 females. The male to female ratio was 0.92.

Age of the patient assorted from 18 to 50 years. The mean age was 42.06 years with standard deviation of 6.55. These findings were consistent with the findings of Xiangming Meng et all 2022 in which average age of the patients were 43.1 years (range 18–67 years).

Out of 100 Post covid-19 patients, majority (40%) of them were having history of moderate covid infection, 38% were having history of mild and only 22% were having history of severe infection according to WHO Guidelines.

The present study showed that out of 100 post covid-19 patients, 5(13.1%) patients were having symptoms who had mild covid infection, 15(37.5%) were having symptoms who had moderate covid infection, whereas 13(59%) patients were having symptoms who had severe covid infection. However, no data is available which compare the severity of covid infection with symptomatology.Even though the probability of steroid injections is very likely in patients with moderate and severe degree of Covid 19 infection but as per history given by the patients none of them received steroid injections and even if they did there was no documentation available with them.

In our study, presenting complain was aural fullness (25%), followed by 20(20%) hearing loss, 9 (9%) presented with tinnitus, 3(3%) were suffering from vertigo, and none of them had facial nerve palsy. Analogous conclusion has been made by Xiangming Meng and Jing Wang et al. 2022 in a systematic review of 23 patients, only 4 (17.4%) presented with HL symptoms solely. Our study revealed that out of 20 patients suffering from hearing loss, majority (65%) of them had bilateral involvement, 25% had right ear involved and only 10% had hearing loss in left. Unlike a study conducted by Xiangming Meng et all 2022 in which out of 23, six were affected on the left side, eight on the right side, and nine had bilateral disease.

All the patients were screened for hearing loss, pure tone audiogram was done at first visit which shows out of 100, 80 patients have hearing within normal limit and rest 20 patients, 15 (15%) were having conductive hearing loss, sensorineural hearing loss was seen in 3% and 2% were having mixed hearing loss.

Similar results were found in a study done by Virginia Fancello et al. 2022 [8] on 63 patients affected by COVID-19 reported a new SNHL onset, degree of hearing loss ranged from mild to moderate in 58.7% of the patients.

Our study revealed that those 20 patients, who were having hearing loss, repeat audiological profile (PTA) was done after interval of 1 month, 13(65%) patients were found to have normal hearing. After 3 months, repeat PTA was done, 18 patients (90%) found to have normal hearing and the remaining 2 patients followed up till 6 months and again PTA was done where only 1 patient was having sensorineural hearing loss.

Almost similar results were found in a study done by Jing wang et al. 2022 [7] that out of those 23 cases of COVID-19- related SSNHL, two patients (8.7%) recovered completely, 12 patients (52.2%) recovered partially, 1 (4.3%) case improved slightly, 6 (26.1%) patients did not improve, one patient (4.3%) recovered completely on one side and partially on the other, and one patient (4.3%) with an unknown outcome.

Conclusion

SARS-CoV-2(Covid-19) has the potential to cause damage to the audio-vestibular system, resulting in SSNHL. However, the exact mechanisms of SARS-CoV-2 on the audio-vestibular system remain unexplained. Our’s was a pilot study done on a limited number of patients due to Covid restrictions. Ideally a larger population needs to be studied, to establish direct association between Covid-19 and SSNHL and understanding the aetiology behind it.