الفهرس 
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Abstract
Summary
Vestibular evoked myogenic potential (VEMP) cervical and ocular, has recently been broadly studied in vestibular disorders. As it is evoked by loud sound stimulation, even mild conductive hearing loss may affect VEMP results. Bone-conducted (BC) stimulus is an alternative stimulation for evoking this response. This study aims to assess the characteristics of BC-VEMP in different groups of patients.
Although air-conducted VEMP (AC-VEMP) can be recorded from patients with profound sensorineural hearing loss, the shortcoming to this method is its susceptibility to even mild conductive hearing loss. That is, as the stimulation threshold of the utricle and saccule is so high, the intensity near the maximum output of a device (i.e.,>90 dBnHL) is applied for its adequate actuation, so, the probability of detecting a VEMP via AC stimulus is dependent on the integrity of sound transmission through the middle ear conductive mechanism to the inner ear. When stimulating sound is attenuated by middle ear pathology, the amount of sound reaching saccule is reduced and VEMP is expected to be poorly elicited .To that end, an accurate vestibular assessment of patients with disequilibrium using AC-VEMP can be challenging when a conductive component of hearing loss is also coexisted.
To overcome this attenuation of stimulation, Bone conduction (BC) stimulation have been proposed as possible solutions to elicit VEMP in CHL. Bone conduction click stimulation can evoke VEMP using frequencies around 500 Hz. Clinical bone vibration generally requires additional amplification to produce strong enough stimuli for VEMP testing.
The aim of the study was to compare amplitude and latency of ocular and cervical vestibular evoked myogenic potentials evoked by air- and bone-conducted stimuli in three different groups.
The study comprised of 30 adults aging from 18 to 50 years old , 10 of them are controls with normal hearing threshold level, 10 patients suffering from different causes that result in conductive hearing loss and 10 patients having sensory neural hearing loss.in the selection of patients, we followed the exclusion criteria in the form of excluding patients with mixed hearing loss.
All patient were subjected to full history taking, pure tone audiogram (PTA), tympanometry, acoustic reflexes , speech reception threshold, word discrimination score, cervical VEMP and Ocular VEMP testing by air and bone stimulation.
The result of this study revealed that percentage of c VEMP and o VEMP waves by AC stimulation and by BC stimulation was 100% in controls and in patients with senorineural hearing loss while percentage of c VEMP and o VEMP waves by AC stimulation is 60 % in patients with CHL and the rate increased to 100% by BC waves. A significant difference existed in the response rate between AC and BC stimulation waves.
There was no statistically significant differences regarding P1 and N1 latencies or amplitude of AC cVEMP between group 1 and group2
While, n1 latency of AC o VEMP in group 2 was delayed than that of group 1 and this difference was statistically significant. with no significant difference in latency from the control group in p1 latency or amplitude of AC o VEMP.
There was no statistically significant differences regarding P1 and N1 latencies or amplitude of BC cVEMP between group 1 and group2 or BC oVEMP n1 and p1 latencies . However amplitude of BC oVEMP n1p1 was statistically significant between group 1 and 2.
There was negative correlation between AC and BC ocular an cervical VEMP latencies and the mean ABG in group 2.
There was no statistically significant differences regarding P1 and N1 latencies of AC cVEMPand AC oVEMP between group 1 and group3
AC c VEMP Amplitude of group 3 was smaller than that of group 1 and this difference was a statistically significant.
There was no statistically significant differences regarding P1 and N1 latencies or amplitude of AC oVEMP between group 1 and group3.
There is a significant correlation between degree of hearing loss and latancy of VEMP waves in SNHL patients.
It can be concluded that conductive hearing loss have impacts on both cervical and ocular VEMPs obtained by air conduction (AC)sound.
BC VEMP provides assessment of vestibular system in patients with conductive hearing loss with high degree of accuracy. There is a correlation between cVEMP and oVEMP abnormalities and severity of sensorineural hearing loss .Vestibular system dysfunction may associate cochlear hearing loss.