[Cervial vestibular-evoked myogenic potential induced by galvanic vestibular stimulation in normal people]

Objective:To establish a new method for detecting vestibular function by testing cervical vestibular-evoked myogenic potential induced by galvanic vestibular stimulation in normal population. Method:Twenty normal ears were tested for cervical vestibular evoked myogenic potential induced by galvanic vestibular stimulation. SPSS 18.0 software was used to analyze the obtained data. Result:In all healthy subjects mastoid-forehead galvanic vestibular stimulation produced a positive-negative biphasic EMG responses on SCM ipsilateral to the cathodal electrode. The latency of p13 was（11.52±3.05） ms. The latency of n23 was（15.31±3.38） ms. The amplitude of p13-n23 was（40.55±27.93） μV. The interval of p13-n23 was（3.53±1.38） ms. The interaural asymmetry ratio（AR, %） of p13, n23 latency, the amplitude and interval were respectively（6.96±6.79）%, （6.47±5.93）%, （28.08±26.42）% and （16.61±11.11）%. There was no significant difference in all parameters between the right and left ears of all subjects. Conclusion:The value of cervical vestibular-evoked myogenic potential induced by galvanic vestibular stimulation in normal subjects can be established to explore methods for diagnosis, treatment and researching mechanism of auditory neuropathy and vestibular neuropathy.

Inner ear test battery in guinea pig models - a review

OBJECTIVE

This study reviewed the development of the inner ear test battery comprising auditory brainstem response (ABR), and caloric, ocular vestibular-evoked myogenic potential (oVEMP), and cervical vestibular-evoked myogenic potential (cVEMP) tests in guinea pig models at our laboratory over the last 20 years. Detailed description of the methodology for testing the small animals is also included.

METHODS

Inner ear disorders, i.e. ototoxicity, noise exposure, or perilymph fistula were established in guinea pig models first. One to four weeks after operation, each animal underwent ABR, oVEMP, cVEMP, and caloric tests. Then, animals were sacrificed for morphological study in the temporal bones.

RESULTS

Inner ear endorgans can be comprehensively evaluated in guinea pig models via an inner ear test battery, which provides thorough information on the cochlea, saccule, utricle, and semicircular canal function of guinea pigs. Coupled with morphological study in the temporal bones of the animals may help elucidate the mechanism of inner ear disorders in humans.

CONCLUSIONS

The inner ear test battery in guinea pig models may encourage young researchers to perform basic study in animals and stimulate the progress of experimental otology which is in evolution.

Otolithic Receptor Mechanisms for Vestibular-Evoked Myogenic Potentials: A Review

Air-conducted sound and bone-conduced vibration activate otolithic receptors and afferent neurons in both the utricular and saccular maculae, and trigger small electromyographic (EMG) responses [called vestibular-evoked myogenic potentials (VEMPs)] in various muscle groups throughout the body. The use of these VEMPs for clinical assessment of human otolithic function is built on the following logical steps: (1) that high-frequency sound and vibration at clinically effective stimulus levels activate otolithic receptors and afferents, rather than semicircular canal afferents, (2) that there is differential anatomical projection of otolith afferents to eye muscles and neck muscles, and (3) that isolated stimulation of the utricular macula induces short latency responses in eye muscles, and that isolated stimulation of the saccular macula induces short latency responses in neck motoneurons. Evidence supports these logical steps, and so VEMPs are increasingly being used for clinical assessment of otolith function, even differential evaluation of utricular and saccular function. The proposal, originally put forward by Curthoys in 2010, is now accepted: that the ocular vestibular-evoked myogenic potential reflects predominantly contralateral utricular function and the cervical vestibular-evoked myogenic potential reflects predominantly ipsilateral saccular function. So VEMPs can provide differential tests of utricular and saccular function, not because of stimulus selectivity for either of the two maculae, but by measuring responses which are predominantly determined by the differential neural projection of utricular as opposed to saccular neural information to various muscle groups. The major question which this review addresses is how the otolithic sensory system, with such a high density otoconial layer, can be activated by individual cycles of sound and vibration and show such tight locking of the timing of action potentials of single primary otolithic afferents to a particular phase angle of the stimulus cycle even at frequencies far above 1,000 Hz. The new explanation is that it is due to the otoliths acting as seismometers at high frequencies and accelerometers at low frequencies. VEMPs are an otolith-dominated response, but in a particular clinical condition, semicircular canal dehiscence, semicircular canal receptors are also activated by sound and vibration, and act to enhance the otolith-dominated VEMP responses.

Vestibular Dysfunctions in Sudden Sensorineural Hearing Loss: A Systematic Review and Meta-analysis

Background

Sudden sensorineural hearing loss (SSHL) not only involves cochlear function but might also be accompanied by vestibular disturbances. The assessment of vestibular function could be of great relevance in SSHL.

Objective

To investigate the prevalence of vestibulocochlear lesions in SSHL and the correlation of specific vestibular organs with hearing prognosis.

Data sources

A complete literature search of eligible studies in the PubMed and EMBASE databases was performed.

Study selection

For our aim, studies that focused on vestibular examination in the case of SSHL were retrieved, including caloric tests, cervical vestibular-evoked myogenic potential (cVEMP) tests, or ocular vestibular-evoked myogenic potential (oVEMP) tests.

Results

Of the 18 studies included, a caloric test was performed in 16 studies, cVEMP in 13 studies, and oVEMP in 5 studies, and together the studies included a total population of 1,468 subjects. The scores on the Agency for Healthcare Research and Quality (AHRQ) questionnaire ranged from 6 to 11. These results indicated that the most commonly damaged vestibular organ in SSHL was the utricle and superior vestibular pathway (U + S) followed by the lateral semicircular canal and superior vestibular pathway (LSC + S), the saccule and inferior vestibular pathway (S + I), and the cochlea only (C only). The meta-analysis indicated that SSHL patients with vertigo have a statistically increased risk of vestibular organ lesions compared with those without vertigo, including the LSC + S subgroup (OR = 4.89, 95% CI = 1.20-19.93, I² = 80%, p = 0.03) and the S + I subgroup (OR = 3.58, 95% CI = 1.61-7.95, I² = 0%, p = 0.002). The pooled possibility of hearing recovery within the LSC + S lesion group was less than half that of the non-LSC + S lesion group (OR = 0.24, 95% CI = 0.11-0.52, I² = 68%, p = 0.0003).

Conclusion

This study shows the relevance of vestibular damage concomitant with SSHL and that SSHL patients with vertigo are at an increased risk of vestibular organ lesions compared with patients without vertigo. LSC + S lesions thus appear to be a critical variable that influence the possibility of hearing improvement in SSHL.

Sensory organization test principally reflects utricular function

CONCLUSION

Our study showed that sensory organization test (SOT) could principally reflect utricular function, and our cut-score of VEST ratio (the indicator of inputs from the vestibular system in balance performance) in SOT could help to screen patients with unilateral peripheral vestibular dysfunction in non-fallers.

OBJECTIVES

We aimed to know SOT reflects the function of which vestibular end organs and to assess the possibility of screening patients with peripheral vestibular dysfunction in non-fall population by means of SOT.

METHODS

A total of 75 patients with unilateral peripheral vestibular dysfunction underwent SOT, ocular vestibular-evoked myogenic potential (oVEMP), cervical vestibular-evoked myogenic potential (cVEMP) and caloric tests.

RESULTS

Regression model indicated that oVEMP, as an independent variable, exerted the greatest influence on VEST ratio, followed by age and cVEMP. There were no significant differences in VEST ratio among groups with different extents of peripheral vestibular involvement (p > .05). VEST ratio in the vestibular impairment groups was significantly lower than in the control group and significantly higher than in fall group (p < .01). VEST ratio in group with normal oVEMP was significantly higher than in group with abnormal oVEMP (p = .013). The cut-score between populations with functional and dysfunctional vestibule was 0.649.

N-acetylcysteine as a single therapy for sudden deafness

CONCLUSION

Like NAC ameliorates hearing loss from acoustic trauma in the inner ear, NAC may also rescue hearing loss from sudden deafness confined to the inner ear.

OBJECTIVE

This study assesses the effect of N-acetyl-L-cysteine (NAC) as a single therapy for sudden deafness.

METHODS

Thirty-five sudden deafness patients with neither systemic disorders nor central signs in electronystagmography were treated with NAC alone and assigned to Group A. For comparison, another 35 sudden deafness patients treated by corticosteroids and plasma expander were assigned to Group B. There were no significant differences between the two groups in terms of age, sex, laterality, and pre-treatment mean hearing level. All patients underwent an inner ear test battery comprising audiometry, and ocular vestibular-evoked myogenic potential (oVEMP), cervical VEMP (cVEMP), and caloric tests.

RESULTS

Groups A and B did not significantly differ in the pre-treatment mean hearing level, and percentages of abnormal oVEMP, cVEMP, and caloric tests, indicating that the involvement severity of sudden deafness between the two groups was similar. However, Group A (43 ± 27 dB) showed significantly greater mean hearing gain than Group B (21 ± 28 dB), and Group A (91%) revealed better improved rate of hearing than Group B (57%).

Acute hearing loss in patients with hematological disorders

OBJECTIVE

This study adopted an inner ear test battery to investigate the causes of acute sensorineural hearing loss in patients with hematological disorders.

METHODS

During the past 20 years, the authors have experienced 14 patients with hematological disorders, i.e. leukemia or aplastic anemia, having acute sensorineural hearing loss. An inner ear test battery comprising audiometry and cervical vestibular-evoked myogenic potential (cVEMP), ocular VEMP (oVEMP), and caloric tests was performed.

RESULTS

Diagnoses comprised of sudden sensorineural hearing loss in 12 patients and endolymphatic hydrops in four patients (two patients had one ear with sudden sensorineural hearing loss while the other ear had endolymphatic hydrops). Percentages of recruitment phenomenon showed a significant difference between endolymphatic hydrops and sudden sensorineural hearing loss. Abnormal percentages for mean hearing level (86%), cVEMP test (71%), oVEMP test (25%), and caloric test (14%) exhibited a significant sequential decline in these patients.

CONCLUSION

Acute sensorineural hearing loss in a patient with leukemia or aplastic anemia may be related to either sudden sensorineural hearing loss or endolymphatic hydrops. A significant sequential decline in the function of the cochlea, saccule, utricle, and semicircular canals indicates that the pars inferior is more vulnerable to blood insult than the pars superior.

Bilateral Meniere's disease assessed by an inner ear test battery

CONCLUSION

An inner ear test battery may suggest bilateral involvement and aid in 'grading' of potential disease in a patient with actively symptomatic Meniere's disease (MD).

OBJECTIVES

This study applied an inner ear test battery in patients with bilateral MD to map the inner ear deficits in each ear.

METHODS

From 2009 to 2012, 100 (20%) of 498 MD patients were diagnosed with bilateral involvement, which was defined as established MD in one ear, and the opposite ear had inner ear symptoms combined with documented hearing loss. Each patient underwent audiometry, and ocular vestibular-evoked myogenic potential (oVEMP), cervical VEMP (cVEMP), and caloric tests.

RESULTS

Grading of inner ear deficits was based on the number of abnormal results in the inner ear test battery. Of 100 patients with bilateral MD, 54% had the same grade and 46% had different grades in their 2 ears. On the other hand, based on four-tone average, 79% had the same Meniere stage and 21% had different stages in their two ears. The difference between ears with asymmetric grades (46%) and ears with asymmetric stages (21%) accounts for 25% of bilateral MD patients, which may be caused by the saccular hydrops in the opposite ear.