ABSTRACT
A negative deflection with a 3-4 ms latency period has been reported to exist within the auditory brainstem response of some patients with profound hearing loss following a strong acoustic stimulus. This deflection, namingly the n3 or the acoustically evoked short latency negative response is assumed to be a vestibular-evoked potential, especially of saccular origin. Since the myogenic potential is also saccular in origin, the purpose of the present study was to investigate the relationship between these two tests in adults with profound hearing loss. The present cross sectional study was performed on 20 profoundly deaf volunteers[39 ears] who aged between 18-40 years old, randomly selected from available deaf adults in Tehran. The auditory brainstem response of all subjects was recorded following a 1000 Hz tone burst in 70-100dB nHL. Subjects were also tested for vestibular evoked myogenic potential. Only 34 of 39 ears recorded myogenic potential that negative response was recorded in 27 of 34 ears with normal p13 and n23. In seven ears with normal p13 and n23, the negative response was absent. In 3 ears with no p13 and n23, the negative response was observed, and two none. In view of the high prevalence of the negative response in profoundly deaf ears with normal p13 and n23, it could be concluded that the negative response can be used when for any reason, it is not possible to record myogenic potential and be considered as a new test in vestibular test battery
ABSTRACT
Contralateral suppression of transient evoked otoacoustic emissions [TEOAEs] test evaluates the efferent auditory system. In this test, acoustic reflex is an important confounding variable. In recent years, application of this test is growing especially in children suspect to central auditory processing disorder. Therefore, the magnitude of influence of this confounding variable on the suppression of TEOAEs should be made clear. The aim of this study was to investigate the impact of acoustic reflex on contralateral suppression of TEOAEs. This research was performed on 39 normal-hearing adults of both sexes and of 18-26 years of age. Tests were used for the determination of interaural attenuation [IA], acoustic reflex, TEOAEs and contralateral suppression of TEOAEs. TEOAEs amplitudes and their contralateral suppression were significantly higher in females and males respectively [p = 0.01]. The amount of TEOAEs suppression before reflex activity ranged between 2000 to 3000 Hz. Activation of acoustic reflex significantly increased the magnitude of suppression in all frequency bands [p
ABSTRACT
Balance disturbance is one of the non-auditory effects of noisy industrial environments that is usually neglected. The aim of the current study was to investigate the effect of occupational noise on vestibular system among workers with noise-induced hearing loss [NIHL], based on both vestibular evoked myogenic potentials [VEMP] and caloric tests. Thirty male workers with noise-induced hearing loss and thirty male matched controls were examined by VEMP and caloric tests. Study parameter included unilateral weakness, p13 and n23 latencies, and p13-n23 amplitude. Caloric test was performed only for 20 patients. No significant difference was observed in unilateral weakness between the two groups. On the other hand, the difference in mean latencies of p13 in the right ear [p= 0.003] and left ear [p=0.01] was significant between the two groups. However, the difference in n23 latency was significant only in the right ear [p=0.03]. There was no significant difference between groups in p13-n23 amplitude. It seems that pars inferior of vestibule is the susceptible part in individuals with NIHL. In general, abnormal findings in both VEMP and caloric tests were more common compared to functional symptoms such as vertigo, which may be due to central compensation and the symmetry of the disorder