We utilized a questionnaire to describe the audiovestibular symptoms in post COVID-19 patients, as well as their demographic features, and the results of their investigations in relation to cochleovestibular manifestations. Overall, the current study found that audiovestibular affection was widespread in the initial phase of COVID-19 infection. During the first four weeks following the first symptom, newly acquired vertigo was the most frequently reported cochleovestibular complaint (20.8%). Patients also reported de novo hearing loss (13.9%), tinnitus (12.7%) and aural fullness (11.4%) with all the symptoms being mostly reported during the first week following onset of the disease (vertigo 62.0%, ear fullness 46.9%, tinnitus 40.9% and hearing loss 32.6%).

Of our patients, 100 (40.8%) experienced vertigo during or after their COVID 19 infection with 21% of them experienced vertigo once, while the rest had vertigo twice or more. Of the patients who experienced vertigo following the infection, 57.1% experienced spontaneous vertigo whereas the rest had positional vertigo. Fifty four percent had vertigo for seconds, 34% for minutes and 9% for hours. Three percent of our sample experienced vertigo for days which could denote an inflammation in the vestibular nerve or vestibular neuritis (VN) [8]. Forty six percent of our sample experienced vertigo similar to Meniere’s disease (ranging from minutes to hours), which could be explained by the immunological theory described by Bumm et al., [12], where T4 T-helper and T8 T-suppressor cells were found in inner ear diseases (e.g., Menière’s disease, sudden hearing loss, vestibular neuritis and Bell’s Palsy) using specific monoclonal antibodies. In a previous study done in 2020, 18.4% of patients reported equilibrium disorders after they were positively diagnosed with COVID-19, where 94.1% of them reported dizziness and 5.9% reported acute attacks of vertigo [19]. The lower percentage of vertigo reported by Viola et al., [19] is probably because the authors did not explain the nature of vertigo to patients (spinning sensation of self or surroundings), which we stressed in our questionnaire to differentiate between vertigo and other balance disorders.

The estimated prevalence of newly acquired hearing loss (13.9%) in this study is higher than a recent study by Almishaal et al., who reported a prevalence of 6.31% in their study, which utilized a questionnaire to assess the short-term and long-term cochleovestibular symptoms following COVID-19 infection in 301 severe hospitalized and mild non-hospitalized patients [20]. Conversely, another study used hearing handicap inventory during convalescence period, and found that hearing loss appeared or worsened in 40% of patients [21]. These differences may be related to differences in the methods and tools used for assessment of symptoms and self-reporting may be associated with over or under reporting.

The prevalence of tinnitus in this study was found to be 12.7% (57.6% unilateral and 42.4% bilateral), which is, yet again, higher than Almishaal et al. (9.97%) [20]. Nevertheless, the frequency of tinnitus as a symptom in case studies of COVID-19 patients seems to be much higher, where a systematic review of auditory disturbances in COVID-19 patients [22] reported four out of 16 patients (25%) (two unilateral and two bilateral) complaining of tinnitus. Conversely Gallus et al., [23] investigated audiovestibular affection in 48 post COVID-19 patients in a retrospective study using pure-tone audiometry thresholds, tympanometry, and Stapedius reflex, and only two patients (4.2%) reported tinnitus. Surprisingly, all the investigations showed normal results and the authors concluded that the symptoms were transient and no permanent audiovestibular damage has occurred.

Ear fullness was reported in 11.4% of our patients which is less than that reported in Almishaal et al., (18.94%) [20]. Similar frequencies of ear fullness in COVID-19 patients were found in previous studies [24, 25].

Presence of the virus in the middle ear and Eustachian tube [15, 26] could explain the intermittent hearing loss and ear fullness experienced by our patients owing to middle ear infection and Eustachian tube dysfunction.

No significant difference was found between study groups and the level of D-dimer (n = 94), however a moderate significantly positive correlation (rs = 0.340, p = 0.001) was found between patients who reported vertigo following COVID-19 infection and the level of their D-dimer, as well as a weak significantly positive correlation between the number of audiovestibular symptoms and the level of D-dimer (rs = 0.147, p = 0.021). D-dimer has been used as an efficient biomarker of thrombotic tendency in COVID-19 patients and has been associated with higher disease severity [27]. The presence of vertigo in COVID-19 patients together with elevated D-dimer levels has been reported in the literature [16]. The formation of microthrombi in the circulation is known to occur during the COVID-19 infection and could explain the occurrence of Benign Paroxysmal Positional Vertigo (BPPV) after the initial phase of the SARS-COVID-19 infection. This might explain the positional vertigo, which was reported in 42.9% of our sample [7]. This theory is supported by our results, which showed a positive correlation between the D-dimer and vertigo (r = 0.340, p = 0.001).

The COVID-19 Reporting and Data System (CO-RADS) can be used, along with certain biochemical markers, as a predictor of ICU admission (94.2% accuracy) in COVID-19 subjects, and therefore is a good indicator of disease severity [28]. When different study groups were compared in terms of CO-RADS grading system, no significant difference was found, nonetheless a weak significantly positive correlation between the number of audiovestibular symptoms and the CO-RADS score (n = 75) (rs = 0.155, p = 0.015).

This study has some limitations. First, COVID-19 severity was not assessed among the survey respondents. Consequently, the severity of the condition could not be linked to the occurrence of audiovestibular symptoms. Second, the patients were not clinically examined yet, our study examines de novo audiovestibular symptoms. Third, the study used online reporting of subjective symptoms which might be affected by other factors such as the recall bias and mental state of the patient.