Sacculo-collic pathway dysfunction accompanying auditory neuropathy

Vestibular and radiological characteristics of children affected by unilateral auditory neuropathy spectrum disorder

OBJECTIVE

Auditory neuropathy spectrum disorders (ANSD) are defined by the association of a preserved outer hair cell function and an impaired auditory nerve neural response, and present mostly bilaterally. Unilateral ANSD are consequently only seldom described, and most frequently as isolated cases. This study aims to describe the audiological, vestibular and radiological characteristics of a population of children with unilateral ANSD.

MATERIAL AND METHODS

We isolated 22 patients with unilateral ANSD, 12 boys and 10 girls from 0 to 95 months, in a database of auditory evoked potentials. We reviewed the audiological, radiological and vestibular assessments. The audiological assessment included tympanometry, otoacoustic emission recording and auditory evoked potential. Otolithic function was assessed by performing cervical vestibular evoked myogenic potential. The canal function was determined by video head impulse test and/or caloric test. The radiological evaluation consisted of an MRI of the internal auditory canal.

RESULTS

Many patients with a type A tympanometry had no response to otoacoustic emission (53,8%), in the presence of a cochlear microphonic potential. Vestibular assessment was performed in 9 of the 22 patients. 4 children had impaired otolithic and/or canal function. MRI evaluation of the inner ear was performed in 18 patients. Aplasia or hypoplasia of the cochlear nerve was found in 17 of them. MRI showed additional vestibular or brainstem abnormalities in 7 of the 18 children. All children with impaired vestibular function had vestibular or brainstem radiological alterations in addition to cochlear branch aplasia or hypoplasia.

CONCLUSIONS

Radiological and vestibular abnormalities are common in children with unilateral ANSD and suggest that a radiological and vestibular assessment is required.

Vestibular dysfunction in patients with auditory neuropathy detected by vestibular evoked myogenic potentials

OBJECTIVES

This study aimed to determine vestibular involvement in patients with auditory neuropathy (AN) using ocular vestibular evoked myogenic potential (oVEMP), cervical vestibular evoked myogenic potential (cVEMP), caloric tests, video Head Impulse Tests (vHIT), and Suppression Head Impulse Paradigm (SHIMP) tests.

METHODS

Twenty-two patients with AN (study group) and 50 age-and-gender-matched healthy subjects (control group) were enrolled. All patients underwent air-conducted sound oVEMP and cVEMP tests. In the study group, 20 patients underwent a caloric test, 10 patients underwent a video Head Impulse Test (vHIT), and nine patients underwent the Suppression Head Impulse Paradigm (SHIMP) test.

RESULTS

Significant differences in VEMP abnormalities were found between the two groups. Most AN patients showed no VEMP response, while only a few patients showed VEMP responses with normal parameters. Some AN patients presented abnormal VEMP parameters, including thresholds, latencies, and amplitudes. The abnormal rate (including no response and abnormal parameters) was 91% in the cVEMP test and 86% in the oVEMP test. No significant difference was found between oVEMP and cVEMP abnormalities. AN patients exhibited a 70% abnormal rate in the caloric test. Most AN patients showed normal VOR gains. Most patients showed no overt corrective saccades in vHIT, and exhibited normal anticompensatory saccades in the SHIMP test.

CONCLUSION

Many AN patients experience vestibular dysfunction, which may be detected by using a vestibular functional test battery.

SIGNIFICANCE

VEMP abnormalities might reflect the status and degree of vestibular involvement in AN.

Methodological aspects of testing vestibular evoked myogenic potentials in infants at universal hearing screening program

Motor development in infants is dependent upon the function of the inner ear balance organ (vestibular organ). Vestibular failure causes motor delays in early infancy and suboptimal motor skills later on. A vestibular test for newborns and infants that is applicable on a large scale, safe and cost effective is in demand in various contexts: in the differential diagnosis of early onset hearing loss to determine forms associated with vestibular failure; in early hearing habilitation with cochlear implant, indicating the vestibular predominant side; and in the habilitation of children affected by motor skill disorders, revealing the contribution of a vestibular failure. This work explored the feasibility of cervical vestibular evoked myogenic potentials (VEMP) in conjunction with newborn universal hearing screening program. VEMP was measured after the hearing tests and was evoked by bone-conducted stimuli. Moreover, stimulus delivery was regulated by neck muscle activity, with infants rested unconstrained in their parents´ arms and with the head supported by the operator´s hand. This VEMP protocol showed a high level of feasibility in terms of test viability and result reproducibility. VEMP integrated into the newborn hearing screening program may represent a practical method for large-scale assessment of balance function in infants.

Saccular dysfunction in children with sensorineural hearing loss and auditory neuropathy/auditory dys-synchrony

CONCLUSION

There is a correlation between the AN/AD disorder and the saccular dysfunction in children with severe sensorineural hearing loss, which means that saccular dysfunction can be a concomitant sign of AN/AD. In conclusion, the term of audio-vestibular dys-synchrony (AVS) is a more suitable description for this condition.

OBJECTIVES

Patients with auditory neuropathy/auditory dys-synchrony (AN/AD) characteristically demonstrate poor neural responses from the vestibulocochlear nerve and brainstem while displaying evidence of intact outer hair cells function. Therefore, the objective of this study is studying of the relationship of the saccular dysfunction with AN/AD disorder in children with sensorineural hearing loss.

METHODS

In this cross-sectional study, 100 children with bilateral severe-to-profound sensorineural hearing losses underwent audiologic tests and cervical vestibular-evoked myogenic potentials (cVEMPs) at the Audiology Department of Hamadan University of Medical Sciences (Hamadan, Iran).

RESULTS

Eleven children with bilateral severe sensorineural hearing loss were given to unilateral AN/AD disorder (11 ears), and two children (4 ears) had bilateral AN/AD (total = 13 children). The ears with AN/AD took the form of unrepeatable or absent waves of ABR and presence of OAEs. The statistical analysis of an independent t-test between AN/AD ears as compared to non-AN/AD ears of these 13 children showed that the mean latencies of p13 and the mean latencies of n23 and the mean peak-to-peak amplitude had significant differences.

Ocular vestibular evoked myogenic potential using different test stimuli

Aim. Ocular Evoked Myogenic Potential (oVEMP) are short latency potentials evoked by higher acoustic stimulation. In this study, we aimed at comparing the click, 500 Hz mixed modulated, and 500 Hz short duration tone burst stimuli using oVEMP. Material. Click, 500 Hz mixed modulated and 500 Hz short duration tone burst stimuli were used for the study. Method. Conventional sampling and conveneint study design were used. Sixty healthy subjects underwent contralateral oVEMP testing maintaining 30 degrees upward gaze. Single channel electrode montage was applied to record oVEMP response. Results. On statistical analysis the three stimuli evoked equal response rates (100%), and when latency of n1 and p1 and peak-peak amplitude were compared, the click evoked showed significantly early latency and lower peak-peak amplitude than the 500 Hz stimuli. Five hundred Hz stimuli did not show significant difference in latency and peak-peak amplitude of n1-p1. Discussion. Thus, 500 Hz stimuli can evoke better latency and peak-peak amplitude. oVEMP has good clinical significance in diagnosing subjects with vestibular dysfunction. To add to the sensitivity of the oVEMP test, 500 Hz stimuli may also be used as it can evoke better oVEMP responses in clinical population with good morphology.

Cervical and Ocular Vestibular Evoked Myogenic Potentials Test Results in Individuals with Auditory Neuropathy Spectrum Disorders

Auditory neuropathy spectrum disorder is a clinical disorder where the outer hair cell functioning is intact but the functioning of the auditory nerve is affected. Since, the 8(th) nerve is constituted by both the auditory and vestibular branch of nerve fibers, there are chances that the vestibular nerve might also be affected. Hence, the current study was carried out in order to determine the functioning of vestibular nerve in individuals with auditory neuropathy. A total of 11 participants were considered for the current study. Cervical vestibular evoked myogenic potentials (cVEMPs) and ocular vestibular evoked myogenic potentials (oVEMPs) were administered using the conventional protocol. In all the participants (100%) the oVEMPs were absent whereas in 20 ears out of 22 ears tested (90.90%) the cVEMPs were absent. The results of the present study indicate a high incidence of vestibular involvement in individuals with auditory neuropathy spectrum disorders. Also, it necessitates the inclusion of vestibular tests in the test battery used to assess individuals with auditory neuropathy spectrum disorder.

Vestibular test findings in individuals with auditory neuropathy: review

Background:

The vestibulocochlear nerve is a sensory nerve that serves the organs of hearing and equilibrium. Neuropathies of the nerve, particularly auditory neuropathy, may be caused by primary demyelination or axonal disease. Cochlear amplification function is normal in cases of auditory neuropathy, but afferent neural conduction in the auditory pathway is disordered. It is highly probable that the vestibular nerve has some involvement in disorders affecting the cochlear nerve.

Objective:

To provide an overview of vestibular test findings in individuals with auditory neuropathy.

Method:

A structured literature search was carried out, with no restrictions to the dates searched.

Conclusion:

Auditory neuropathy implicated the vestibular branch of the VIIIth cranial nerve as well as the cochlear nerve. However, there was variability in terms of vestibular test findings.

Comparison of vestibular evoked myogenic potentials elicited by click and short duration tone burst stimuli

Introduction:

Vestibular evoked myogenic potentials are short latency electrical impulses that are produced in response to higher level acoustic stimuli. They are used clinically to diagnose sacculocollic pathway dysfunction.

Aim:

This study aimed to compare the vestibular evoked myogenic potential responses elicited by click stimuli and short duration tone burst stimuli, in normal hearing individuals.

Method:

Seventeen subjects participated. In all subjects, we assessed vestibular evoked myogenic potentials elicited by click and short duration tone burst stimuli.

Results and conclusion:

The latency of the vestibular evoked myogenic potential responses (i.e. the p13 and n23 peaks) was longer for tone burst stimuli compared with click stimuli. The amplitude of the p13–n23 waveform was greater for tone burst stimuli than click stimuli. Thus, the click stimulus may be preferable for clinical assessment and identification of abnormalities as this stimulus has less variability, while a low frequency tone burst stimulus may be preferable when assessing the presence or absence of vestibular evoked myogenic potential responses.

Vestibular evoked myogenic potential (VEMP) in patients with auditory neuropathy: Auditory neuropathy or audiovestibular neuropathy?

CONCLUSION

Our results suggest that isolated auditory or vestibular involvement is unlikely and in fact audiovestibular neuropathy can better explain auditory neuropathy.

OBJECTIVE

The purpose of this study was to investigate saccule and related neural pathways in auditory neuropathy patients.

METHODS

Three males and five females diagnosed with auditory neuropathy were included in this prospective study. Patients' ages ranged from 21 to 45 years with a mean age of 28.6 ± 8.1 years and the history of disease was between 4 and 19 years. A group of 30 normal subjects served as the control group. The main outcome measures were the mean peak latency (in ms) of the two early waves (p13 and n23) of the vestibular evoked myogenic potential (VEMP) test in patients and controls.

RESULTS

Of the 8 patients (16 ears), normal response was detected in 3 ears (1 in right and 2 in left ears). There were unrepeatable waves in four ears and absent VEMPs in nine ears.

Vestibular nerve functions in children with auditory neuropathy

In disorders affecting the cochlear nerve it is highly probable that the vestibular nerve is involved as well. The caloric test and VEMP (vestibular evoked myogenic potentials) enable a separate evaluation of the inferior and superior vestibular nerve. In the present study we evaluated the inferior and superior vestibular nerves in three children with auditory neuropathy. Electrophysiological tests, VEMP and caloric tests were carried out in these three cases with the preliminary diagnosis of auditory neuropathy. Magnetic resonance imaging was obtained which revealed an intact cochlear nerve in all three patients. The caloric tests were all normal, while in two out of the three cases the VEMP test yielded abnormal results. Since the caloric test may prove abnormal as well, as reported in the literature, it would be valuable to carry out both of the tests in the vestibular evaluation of children with auditory neuropathy, in our opinion.

Diagnostik und Therapie der auditorischen Synaptopathie/Neuropathie

Pathological auditory brainstem responses (lack of responses, elevated thresholds and perturbed waveforms) in combination with present otoacoustic emissions are typical audiometric findings in patients with a hearing impairment that particularly affects speech comprehension or complete deafness. This heterogenous group of disorders first described as "auditory neuropathy" includes dysfunction of peripheral synaptic coding of sound by inner hair cells (synaptopathy) and/or of the generation and propagation of action potentials in the auditory nerve (neuropathy). This joint statement provides prevailing background information as well as recommendations on diagnosis and treatment. The statement focuses on the handling in the german language area but also refers to current international statements.

Vestibular evoked myogenic potentials

PURPOSE OF REVIEW

Vestibular evoked myogenic potential testing is the only clinically feasible way to measure function of the saccule. Interest in this test has exploded in recent years because of its potential utility in diagnosing third-window disorders and in diagnosing and monitoring Ménière's disease.

RECENT FINDINGS

Recent literature on vestibular evoked myogenic potential covers a wide range of topics. Review articles, method articles and many case reports and uncontrolled case series are seeking new applications for vestibular evoked myogenic potential in diagnosis and monitoring of neurotologic disease, and in shedding light on inner ear diseases by mapping anatomic sites of involvement. The most informative work is still in the areas of superior semicircular canal dehiscence and in Ménière's disease. Also, many aspects of vestibular evoked myogenic potential and its use have not yet been adequately studied or described.

SUMMARY

Vestibular evoked myogenic potential is a new test of saccular and inferior vestibular nerve integrity. It holds great promise for diagnosing and monitoring Ménière's disease and some other neurotologic disorders. It is still an evolving field, however. The methods, equipment, and applications for vestibular evoked myogenic potential testing are not yet standardized. It is not yet time for this test to be widely applied, but that time is not far off.