Background: World Health Organization (WHO) officially announced the COVID-19 epidemic as a pandemic. Coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered coronavirus. Little direct evidence suggests a viral cause for labyrinthitis; however, a wealth of epidemiologic evidence implicates several viruses as potentially causing inflammation of the labyrinth. Viral labyrinthitis is often preceded by an upper respiratory tract infection and occurs in epidemics.
Aims/Objectives: This study compared latencies of vestibular evoked myogenic potentials (VEMPs) between asymptomatic COVID-19 PCR-positive cases and normal non-infected subjects.
Material & methods: Twenty cases who were confirmed positive for COVID-19 and had none of the known symptoms for this viral infection formed the test group for 2 full weeks. Their age ranged between 20-50 years to avoid any age-related hearing affection. Patients who had definite symptoms of COVID-19 infection as well as those who had a history of hearing loss or a history of any known cause of hearing loss were excluded from the examined sample. VEMPs latencies were measured for all participants.
Results: Deterioration of saccular hair cell functions was detected by the significantly increased latency of the VEMPs compared to controls.
Conclusions and significance: COVID-19 infection could have drastic effects on vestibular hair cell functions despite being asymptomatic. COVID-19 patients should be followed up to detect any complaints regarding their vestibular performance. The mechanism of these effects requires further research.
Keywords:COVID-19; Corona virus; VEMP; Vestibular function
An acute respiratory disease, caused by a novel coronavirus (SARS-CoV-2, previously known as 2019-nCoV), the coronavirus disease 2019 (COVID-19) has spread throughout China and received worldwide attention. On 30 January 2020, World Health Organization (WHO) officially declared the COVID-19 epidemic as a public health emergency of international concern. Coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered coronavirus. Most people infected with the COVID-19 virus experience mild to moderate respiratory illness and recover without requiring special treatment .
COVID-19 infection symptoms may appear 2-14 days after exposure (based on the incubation period of COVID-19 virus). The clinical symptoms of COVID-19 patients include fever, cough,
fatigue, and a small population of patients had gastrointestinal infection symptoms. The elderly and people with underlying diseases are susceptible to infection and prone to serious outcomes, which may be associated with acute respiratory distress syndrome (ARDS) and cytokine storm [1,2]. Currently, there are few specific antiviral strategies, but several potent candidates of antivirals and repurposed drugs are under urgent investigation. There are multiple scenarios COVID-19 patients may follow: Some get serious respiratory distress, some improve with medical treatment, the rest recover with no intervention .
Viral infections can cause congenital and acquired hearing loss. Rubella and cytomegalovirus are the best-recognized viral causes of prenatal hearing loss. Virally induced hearing loss in the postnatal period is usually due to mumps or measles. Viral infections are also implicated in idiopathic, sudden sensorineural
hearing loss (SNHL). Experimental evidence suggests that
inflammatory proteins play a critical role in the pathogenesis of
cytomegalovirus-induced hearing loss .
A unique form of viral labyrinthitis is herpes zoster oticus, or
Ramsay-Hunt syndrome. The cause of this disorder is reactivation
of a latent varicella-zoster virus infection occurring years after
the primary infection. Evidence suggests that the virus may attack
the spiral and vestibular ganglion in addition to the cochlear and
vestibular nerves . Auditory and vestibular symptoms develop
in approximately 25% of patients with herpes oticus, in addition
to the facial paralysis and vesicular rash that characterize the
Little direct evidence suggests a viral cause for labyrinthitis;
however, a wealth of epidemiologic evidence implicates several
viruses as potentially causing inflammation of the labyrinth.
Viral labyrinthitis is often preceded by an upper respiratory tract
infection and occurs in epidemics. The histologic finding of axonal
degeneration in the vestibular nerve suggests a viral etiology for
vestibular neuritis .
Potential viral causes of labyrinthitis include the following:
b) Mumps virus
c) Varicella-zoster virus
d) Rubeola virus
e) Influenza virus
f) Parainfluenza virus
g) Rubella virus
h) Herpes simplex virus 1
k) Respiratory syncytial virus
Asymptomatic infection at time of laboratory confirmation
has been reported from many settings ; a large proportion
of these cases developed some symptoms at a later stage of
infection. There are, however, also reports of cases remaining
asymptomatic throughout the whole duration of laboratory
and clinical monitoring. Viral RNA and infectious virus particles
were detected in throat swabs from some COVID-19 patients, but
they developed none of the symptoms listed above . Although
several viral infections may lead to hearing loss only or as a part
of a labyrinthitis, it is still unknown whether COVID-19 has effects
on the vestibular system or not. Therefore, this research was
designed to address the impact of this novel viral infection on the
saccular vestibular system.
Twenty cases who were confirmed positive for COVID-19 and
had none of the known symptoms for this viral infection formed
the test group for 2 full weeks. Their age ranged between 20-50
years to avoid any age-related hearing affection. Patients who had
definite symptoms of COVID-19 infection as well as those who
had a history of hearing loss or a history of any known cause of
hearing loss were excluded from the examined sample. Twenty
subjects who had normal hearing (All subjects had audiometric
thresholds at or better than 15dB HL) with no history of a known
cause of hearing loss were used as a control group.
All the following procedures was conducted for both study
(at the 14th day after being confirmed COVID-19 positive but
asymptomatic) and control groups:
a) Meticulous history taking and full ENT examination
were carried out on all subjects before audiological testing
b) Basic Audiological evaluation. Audiometric thresholds
were measured using a calibrated Amplaid 309 clinical audiometer
. Air conduction thresholds were measured for frequencies
from 250 to 8000Hz using Telephonics TDH39 earphones. Bone
conduction thresholds were obtained for frequencies from 250
to 4000Hz using a Radio Ear B71 bone vibrator. The audiometric
thresholds were measured using the modified Hughson-Westlake
c) Immittance evaluation. Tympanometry was carried out
using an Amplaid 775 middle ear analyzer to rule out middle ear
d) Vestibular evoked myogenic potentials. Vestibular
evoked myogenic potentials (VEMPs) were recorded in all
subjects using an evoked potential system Spirit Nicolet. Monaural
alternating acoustic click stimuli at an intensity of 90dB nHL were
used. EMG activity was recorded on the sternocleidomastoid
muscles (SCM) with the patient in the sitting position. The mean
peak latency (in ms) of the two early waves (P13-N23) of the VEMP
An informed consent was obtained from all participants. The
study was approved from the Egyptian Central Unit of Medical
Service (ECUMS). EMMS also helped the research team to
connect with the study subjects. EMMS secured a totally aseptic
environment for this research including subjects and equipment.
Paired t-test test was used to compare the pure-tone thresholds
between the test and the control groups. No significant difference
(p> 0.05) was found at all octave and mid-octave frequencies (250,
500, 750, 1000, 1500, 2000, 3000), 4000. Significant difference
was found (P< 0.05) at 4000,6000, and 8000Hz between both
groups (Figure 1).
Paired t-test was used to compare the VEMPs latencies of
waves P13 and N23 among the control and test groups. A highly
significant (p< 0.001) difference was found between the control
group and the test groups (Figure 2).
A highly significant (p< 0.001) difference was found between
the control group and the test groups as regards the latencies of
VEMPs P13 & N23 latency average. The high frequency pure-tone
thresholds were significantly worse in the test group. Similar
results of a previous study showed that COVID-19 infection had
deleterious effects on the hair cells in the cochlea . Moreover,
the absence of the major symptoms does not guarantee a safe
healthy labyrinthine function. The damage to the outer hair
cells was evidenced by the reduced amplitude of the TEOAEs in
test group when compared with control group. Additionally, the
harm to the saccular vestibular cells was detected by the marked
delayed VEMPs waves.
Auditory system damage secondary to viral infections is
typically intracochlear or intralabyrinthine; however, some
viruses can affect the auditory brainstem as well. Mechanisms
of injury to the peripheral auditory system can include direct
viral damage to the organ of Corti, stria vascularis, or spiral
ganglion; damage mediated by the patient’s immune system
against virally expressed proteins (Cytomegalovirus); and
immunocompromise leading to secondary bacterial infection
of the ear (Human Immunodeficiency Virus & measles) . The
deterioration saccular vestibular functions could be attributed
to the generalized damaging effects of the viral infection on the
labyrinthine hair cells, but the mechanism is still unknown. The
results of the present study also demonstrated that the absence
of major symptoms may hide unknown impact on the delicate
sensory organs taking the labyrinth as an example.
In conclusion, COVID-19 infection could have drastic effects on
saccular vestibular hair cell functions despite being asymptomatic.
The mechanism of these effects requires further research as well
as close follow-up.
I am deeply grateful to Egyptian Central Unit of Medical
Service (ECUMS). I am also thankful for the technical support
of Sigma incorporation for Audiological Services and the great
help and cooperation of Dr. Marwa El Hawary (Alfayoum general
hospital) in conducting this research.