Vestibular Findings Associated with Chronic Noise Induced Hearing Impairment

Abstract

Histological and functional derangements of the vestibular system have been reported in laboratory animals exposed to high levels of noise. However, clinical series describe contradictory results with regard to vestibular disturbances in industrial workers and military personnel suffering from noise induced hearing loss (NIHL). The purpose of the present study was to evaluate vestibular function in a group of subjects with documented NIHL, employing electronystagmography (ENG) and the smooth harmonic acceleration (SHA) test. Subjects were 22 men suffering from NIHL and 21 matched controls. Significantly lower vestibulo-ocular reflex gain (p = 0.05), and a tendency towards decreased caloric responses were found in the study group. No differences in the incidence of vertigo symptoms, spontaneous, positional and positioning nystagmus, directional preponderance and canal paresis in the ENG, or the SHA test phase and asymmetry parameters were observed between the groups. These results demonstrated a symmetrical centrally compensated decrease in the vestibular end organ response which is associated with the symmetrical hearing loss measured in the study group. Statistically significant correlations were found between the average hearing loss, the decrement in the average vestibulo-ocular reflex gain (p = 0.01), and ENG caloric lateralization (p = 0.02). These correlations might indicate a single mechanism for both cochlear and vestibular noise-induced injury. The results imply subclinical, well compensated malfunction of the vestibular system associated with NIHL.

Vestibular evoked myogenic potential in noise-induced hearing loss

“…Golz et al had reported that noise results in asymmetrical or symmetrical hearing loss with abnormal vestibular functions. [2][3][4] Exposure to industrial solvents and noise can have an adverse effect on hearing and balance mechanisms in humans and animals. [5,6] Body sway increases in patients with noise-induced hearing loss (NIHL) suggesting sub-clinical disturbances of the vestibular system.…”

Vestibular Evoked Myogenic Potentials in Acute Acoustic Trauma

“…Conventional VEMP test using 95 dB HL acoustic stimuli for 200 consecutive responses in 40 seconds will not cause temporary threshold shifts of the hearing. However, if higher intensity noise persists, both cochlea and saccule may be damaged because anatomical proximity of the saccule to the stapedial footplate points to the possibility of acoustic trauma associated with saccular dysfunction (8). Therefore, it was the authors' premise that abnormal VEMPs after acute acoustic trauma may be caused by saccular damage from very high intensity noise; consequently, irreversible HL ensued.…”

“…Hence, intense sound and vibration can induce vestibular reflexes, whereas the vestibular fibers are also able to respond to sound (5,6). Accordingly, acoustically responsive saccular afferents trigger acoustic reflexes of the sternocleidomastoid (SCM) muscle, and measurement of such reflexes may reflect the saccular function (7,8).…”

Analysis of Vestibular Evoked Myogenic Potentials and Electrocochleography in Noise Induced Hearing Loss

“…Early studies showed that the sacculus and the cochlea (pars inferior) can be affected by noise, whereas the utriculus and semicircular canal are not [2,3,13,14] . There is no postmortem study on the sacculus's involvement in NIHL.…”

“…Cochlear damage caused by acoustic trauma usually results in hearing loss and tinnitus. Similar to the effects of acoustic trauma on the cochlea, some parts of the vestibular system, such as the sacculus, may also be affected [1,2] . In this circumstance, vestibular symptoms can appear but may be neglected [3,4] .…”