Evaluation of peripheral and central auditory systems of individuals with COVID-19 using test battery approach

In the literature, studies with control groups comparing the auditory systems of individuals with and without COVID-19 use few audiological tests and present inconsistent results. In addition, many studies only examine short-term auditory effects. The first aim of this study was to compare the peripheral-to-central hearing system of people with COVID-19 to an age-sex matched control group using an extensive battery of audiological tests. The study's second aim is to examine the possible long-term effect of COVID-19 on the hearing system by comparing the audiological test results of people who have had COVID-19 in the first three months with the audiological test results after six months. The research group of the study consisted of 30 individuals aged 20-55 years who had outpatient COVID-19 with mild symptoms, and the control group consisted of 30 healthy individuals aged 20-55 years who did not have COVID-19. The first measurement of the COVID-19 group was performed between the first and third months of PCR positive, and the second was performed after the sixth month of PCR positive. The audiological test battery consists of Pure Tone Audiometry, Extended High Frequency Audiometry, Speech Audiometry, Monosyllabic Word Recognition Test in Noise, Masking Level Difference Test, Immitansmetric Examination, Transient Evoked Otoacoustic Emission Test, Contralateral Suppression Test, Auditory Brainstem Response and Middle Latency Response. Statistically significant differences were observed between the group with COVID-19 and the control group in terms of extended high-frequency thresholds (EHFT) in the right ear 10 kHz (p=0.007), 12.5 kHz (p=0.028) and left ear 10 kHz (p=0.040), 12.5 kHz (p=0.040). EHFT is higher in the group with COVID-19. To investigate a possible ototoxicity in the difference seen, the extended high frequency thresholds of individuals with and without favipiravir were compared. There was no statistically significant difference between the favipiravir and non-treated groups at 10, 12.5, and 14 kHz frequencies in both ears (p>0.05). There was no significant difference between the groups for other audiological tests performed to evaluate the peripheral and central auditory system (p>0.05). There was a statistically significant difference in the 500 Hz hearing threshold of the right ear between the test results of the COVID-19 group between the 1st and 3rd month and the test results after the 6th month (p=0.020), and the difference was not considered clinically significant. There was no statistically significant difference between the first and second measurements for other audiologic tests (p>0.05). Based on the difference in the study results, it is thought that adults aged 20-55 years who have experienced COVID-19 as outpatients with mild symptoms may have damage in the basal part of the cochlea. Since this effect cannot be detected by conventional audiological evaluation, it is recommended that Extended High Frequency Audiometry be performed in people who have had COVID-19. As a result of all evaluations, no other findings were found to support that the afferent and efferent central auditory system was affected. It should not be ignored that the results may differ in the population with severe disease and in different age groups.