A 'neural' response with 3-ms latency evoked by loud sound in profoundly deaf patients

Vestibular-Evoked Cerebral Potentials

The human vestibular cortex has mostly been approached using functional magnetic resonance imaging and positron emission tomography combined with artificial stimulation of the vestibular receptors or nerve. Few studies have used electroencephalography and benefited from its high temporal resolution to describe the spatiotemporal dynamics of vestibular information processing from the first milliseconds following vestibular stimulation. Evoked potentials (EPs) are largely used to describe neural processing of other sensory signals, but they remain poorly developed and standardized in vestibular neuroscience and neuro-otology. Yet, vestibular EPs of brainstem, cerebellar, and cortical origin have been reported as early as the 1960s. This review article summarizes and compares results from studies that have used a large range of vestibular stimulation, including natural vestibular stimulation on rotating chairs and motion platforms, as well as artificial vestibular stimulation (e.g., sounds, impulsive acceleration stimulation, galvanic stimulation). These studies identified vestibular EPs with short latency (<20 ms), middle latency (from 20 to 50 ms), and late latency (>50 ms). Analysis of the generators (source analysis) of these responses offers new insights into the neuroimaging of the vestibular system. Generators were consistently found in the parieto-insular and temporo-parietal junction-the core of the vestibular cortex-as well as in the prefrontal and frontal areas, superior parietal, and temporal areas. We discuss the relevance of vestibular EPs for basic research and clinical neuroscience and highlight their limitations.

Grades of hearing loss affect the presence of acoustically evoked short latency negative responses in children with large vestibular aqueduct syndrome

OBJECTIVES

We aimed to investigate the relationship between grades of hearing loss and the presence of acoustically evoked short latency negative response (ASNR) in children with large vestibular aqueduct syndrome (LVAS), so as to enhance the reference value of ASNR for the diagnosis of LVAS in children.

METHODS

Two hundred sixteen ears from 108 patients (aged 4-90 months) diagnosed with bilateral LVAS, with slight to profound hearing loss, were enrolled in the present study from January 2012 to December 2018. All of the cases were diagnosed with LVAS according to high-resolution computed tomography (HRCT) or magnetic resonance imaging (MRI) scans of the inner ears. The auditory brain stem response (ABR) tests were performed on these subjects with click stimulus (ck-ABR), and the ASNRs were detected based on the method recommended by previous studies. The degree of hearing loss for each ear was classified by the estimated pure-tone average (PTA) thresholds, which were calculated according to the ck-ABR thresholds.

RESULTS

ASNRs were present in 40.7% (88/216) ears during ck-ABR tests. Both thresholds of ABR (Z = 2.977, p = 0.003) and estimated PTA (Z = 2.977, p = 0.003) were significantly higher in the ASNR absent group than in the ASNR present group. The frequency of not profound hearing impairment (≤80 dB HL) was much higher in the ASNR present group (44/88; 50%) than in the ASNR absent group (40/128; 31.3%) (χ² = 7.714, p = 0.005). The results of the logistic regression model, adjusted by cases' age and gender, showed that compared with those ears with profound hearing impairment (>80 dB HL), the not profound impaired ears were associated with a 2.48-fold increased odds of recording ASNR presence in the ck-ABR test [odds ratio (OR) = 2.48, 95% confidence interval (CI): 1.38-4.46, p = 0.003].

CONCLUSIONS

Grades of hearing loss affect the presence of ASNR in children with LVAS, and manifesting as cases with not profound hearing impairment showed increased odds of recording ASNR in the ck-ABR test. Furthermore, more studies should be performed imperatively to determine the diagnosis value of ASNR in children with LVAS.

The acoustically evoked short latency negative response (ASNR) in a unilaterally deaf cat with histologically-confirmed cochleosaccular degeneration

Background

A negative potential is occasionally recorded in humans and animals with profound deafness during brainstem auditory evoked potential (BAER) tests if loud intensities are used. This acoustically evoked short latency negative response (ASNR) is hypothesized to be of saccular origin. The sensitivity to sound of vestibular end organs is also used to produce vestibular evoked myogenic potentials (VEMP), a test that evaluates vestibular function. The same saccular origin is accepted also for VEMP.

Case presentation

A neutered male white domestic short hair cat presented with profound deafness and an ASNR in the left ear during BAER test performed when he was 8 months old. BAER tracings were substantially unchanged at the age of 12 years, immediately before euthanasia that was requested by the owner for the presence of an unrelated neoplastic disorder. The cat underwent a complete post-mortem necropsy including histopathology of the middle and inner ears. Histopathologic results confirmed the presence of a cochleosaccular degeneration of the left ear while the cochlea and sacculus of the right ear and the utriculus and semicircular canals of both ears were histologically normal.

Conclusions

This case report describes the auditory and histopathologic findings of a cat that showed an ASNR during BAER test despite the presence of cochleosaccular deafness. These results confirm that a saccular origin for the ASNR in this case, and in general in cats and dogs with congenital deafness associated with white pigmentation, is improbable. The hypothesis that the sacculus is the vestibular end organ responsible for the generation of the ASNR and VEMP in humans comes mainly from animal studies. The findings in this report may change the clinical interpretation of the results of BAER and VEMP not only in companion animals, but in humans as well.

Uncovered p1 and p2 waves preceding the N3 vestibular evoked neurogenic potential in profound sensorineural hearing loss

Background

The N3 wave is a vestibular evoked neurogenic potential detected in some patients with profound sensorineural hearing loss (PSNHL) during brainstem auditory evoked potential (BAEP) analysis. In 1998, Kato et al. mentioned two electropositive waves preceding N3, which we named p1‐p2, but no further description was given.

Objective

We sought to demonstrate the reproducibility of these waves and hypothesize on their anatomic origin.

Methods

We used two cohorts of patients with PSNHL. The first cohort comprised 10 patients with N3, allowing us to establish a new test with adequate electrophysiological conditions headed to detect p1‐p2 waves (PN3EP). The second cohort consisted of two groups: group A comprised 10 patients in whom N3 was not detected; and group B comprised 20 patients presenting N3. PN3EP was performed in both groups, of which 50% had cervical myogenic vestibular evoked potentials (cVEMPs).

Results

Only group B presented p1‐p2. The PN3EP facilitated the identification of p1‐p2 over BAEP analysis, and their presence correlated well with cVEMPs.

Conclusions

P1‐p2 may be covered due to inadequate BAEP setting conditions, and could be generated in the distal neural path that generates the N3 wave.

The Contributions of Vestibular Evoked Myogenic Potentials and Acoustic Vestibular Stimulation to Our Understanding of the Vestibular System

Vestibular-evoked myogenic potentials (VEMPs) are short-latency muscle reflexes typically recorded from the neck or eye muscles with surface electrodes. They are used clinically to assess otolith function, but are also interesting as they can provide information about the vestibular system and its activation by sound and vibration. Since the introduction of VEMPs more than 25 years ago, VEMPs have inspired animal and human research on the effects of acoustic vestibular stimulation on the vestibular organs, their projections and the postural muscles involved in vestibular reflexes. Using a combination of recording techniques, including single motor unit recordings, VEMP studies have enhanced our understanding of the excitability changes underlying the sound-evoked vestibulo-collic and vestibulo-ocular reflexes. Studies in patients with diseases of the vestibular system, such as superior canal dehiscence and Meniere's disease, have shown how acoustic vestibular stimulation is affected by physical changes in the vestibule, and how sound-evoked reflexes can detect these changes and their resolution in clinical contexts. This review outlines the advances in our understanding of the vestibular system that have occurred following the renewed interest in sound and vibration as a result of the VEMP.

The N3 potential and the efferent cochlear pathway in profound sensorineural hearing loss

OBJECTIVE

This study aimed to evaluate the presence of the N3 potential (acoustically evoked short latency negative response) in profound sensorineural hearing loss, its association with the cervical vestibular evoked myogenic potential and the relationship between both potentials and loss of auditory function.

METHODS

Otological examinations of 66 ears from 50 patients aged from 4 to 36 years were performed, and the vestibular evoked myogenic potential and auditory brainstem response were measured.

RESULTS

The N3 potential was recorded in 36 out of 66 ears (55 per cent) and a vestibular evoked myogenic potential was recorded in 34 (52 per cent). The N3 potential was recorded in 23 out of 34 ears (68 per cent) with a vestibular evoked myogenic potential response and absent in 19 out of 32 ears (59 per cent) without a vestibular evoked myogenic potential response. The presence of an N3 potential was significantly associated with a vestibular evoked myogenic potential response (p = 0.028), but there was no significant difference in the latency or amplitude of the N3 potential in either the presence or absence of a vestibular evoked myogenic potential.

CONCLUSION

The presence of an N3 potential in profound sensorineural hearing loss with good or poor vestibular function can be explained by the contribution of the efferent cochlear pathway through olivocochlear fibres that join the inferior vestibular nerve. This theory is supported by its early latency and reversed polarity, which is masked in normal hearing by auditory brainstem response waves.

A positive wave at 8 ms (P8) and modified auditory brainstem responses measurement in auditory neuropathy spectrum disorder

OBJECTIVE

Auditory neuropathy spectrum disorder (ANSD) is characterized by absent or atypical auditory brainstem responses (ABR), recordable otoacoustic emissions and/or cochlear microphonics. Modification of ABR stimuli is discussed to improve wave V synchronization in ANSD patients.

DESIGN

Ten ANSD children (seven unilateral) underwent ABR measurement with an alternating stimulus (40.5s(-1)), constant rarefaction and condensation stimuli, a reduced click-rate (11.1s(-1)) and a chirp-stimulus.

RESULTS

The results showed no remarkably better synchronization with modified stimuli. Whereas higher levels showed no synchronization, reproducible positive waves at 8 ms (P8) at intensities of 65-85 dB were found in six patients with all stimuli.

CONCLUSIONS

We suggest an ipsilateral auditory origin of the positive potentials at 8 ms. They could be characteristic of synchronization abnormalities in some cases of ANSD.

Acoustically evoked, short latency negative response in children with sensorineural hearing loss

Introduction:

The auditory brainstem response consists of fast and slow waves. The acoustically evoked, short latency negative response is a large, negative deflection with a latency of 3 milliseconds which has been reported in patients with profound hearing loss. It may be of vestibular, particularly saccular, origin, as is the vestibular evoked myogenic potential.

Purpose:

To assess the presence of acoustically evoked, short latency negative responses in children with severe to profound sensorineural hearing loss.

Materials and methods:

Twenty-three children (46 ears) with sensorineural hearing loss underwent audiological evaluation and auditory brainstem response, vestibular evoked myogenic potential and caloric testing.

Results:

An acoustically evoked, short latency negative response was present in 30.43 per cent of ears and absent in 69.57 per cent. Vestibular evoked myogenic potentials were recorded in all ears in the former group, but in only 53.13 per cent in the latter group. Caloric testing was normal in 82.6 per cent of the total ears tested.

Conclusion:

The presence of an acoustically evoked, short latency negative response is dependent not on residual hearing but on normal saccular function. This response can be measured in patients who cannot contract their neck muscles.

Vestibular evoked myogenic potentials in normal mice and Phex mice with spontaneous endolymphatic hydrops

OBJECTIVE AND BACKGROUND

Vestibular evoked myogenic potentials (VEMPs) have been recorded from the neck musculature and the cervical spinal cord in humans and a limited number of laboratory animals in response to loud sound. However, the mouse VEMP has yet to be described. Evaluation of the sacculocollic pathway via VEMPs in mice can set the stage for future evaluations of mutant mice that now play an important role in research regarding human auditory and vestibular dysfunction.

MATERIALS AND METHODS

Sound-evoked potentials were recorded from the neck extensor muscles and the cervical spinal cord in normal adult mice and in circling Phex(Hyp-Duk/y) mice with known vestibular abnormalities, including endolymphatic hydrops (ELH).

RESULTS

Biphasic potentials were recorded from all normal animals. The mean threshold of the VEMP response in normal adult mice was 60 dB normal hearing level with a mean peak latency of 6.25 +/- 0.46 and 7.95 +/- 0.42 milliseconds for p1 and n1 peaks, respectively. At the maximum sound intensity used (100 dB normal hearing level), 4 of 5 Phex mice did not exhibit VEMP responses, and 1 showed an elevated threshold, but normal response, with regard to peak latency and amplitude. The histologic findings in all of these Phex mice were consistent with distended membranous labyrinth, displaced Reissner membrane, ganglion cell loss, and ELH.

CONCLUSION

This is the first report of VEMP recordings in mice and the first report of abnormal VEMPs in a mouse model with ELH. The characteristics of these potentials such as higher response threshold in comparison to auditory brainstem response, myogenic nature of the response, and latency correlation with the cervical recording (accessory nerve nucleus) were similar to those of VEMPs in humans, guinea pigs, cats, and rats, suggesting that the mouse may be used as an animal model in the study of VEMPs. The simplicity and reliability of these recordings make the VEMP a uniquely informative test for assessing vestibular function, and these results suggest that they may be informative in mice with various mutations. However, further investigation is necessary.

N3 potentials in response to high intensity auditory stimuli in animals with suspected cochleo-saccular deafness

We describe a previously un-reported vertex-negative potential evoked by high intensity click auditory stimuli in some dogs and cats with suspected cochleo-saccular deafness. Brainstem auditory evoked potential tracings from 24 unilaterally or bilaterally deaf animals, 22 dogs and 2 cats, among which 21 belonged to breeds with high prevalence of suspected or histologically confirmed cochleo-saccular deafness, were studied retrospectively. Values for latency, amplitude and threshold of this potential in dogs were 2.15+/-0.23 ms, 0.49+/-0.25 microV, and 91.9+/-4.7 dB NHL, respectively (mean+/-SD). Latency and threshold values in cats were in the mean+/-2 SD range of the dog values. Sensitivity to click stimulus polarity and to click stimulus delivery rate pointed towards a neural potential instead of a receptor potential. The vertex-negative wave observed in these animals shares all characteristics with the N3 potential described in some deaf humans with cochlear deafness, where it is presumed to arise from saccular stimulation. The combined degeneration of cochlea and sacculus usually reported in deaf white dogs and cats suggest that N3 may have a different origin in these species.

Sound-evoked neurogenic responses with short latency of vestibular origin

OBJECTIVE

In ABR recording, a large negative deflection with a latency of 3 ms (N3) has been recorded in patients with peripheral profound deafness. It has been suggested that N3 might be of vestibular origin. So far, N3 has been recorded only in patients with peripheral profound deafness. If we can record N3 potentials in subjects with preserved hearing, recording N3 potentials might be a new clinical test of the vestibular system. To record neurogenic potentials (N3) of vestibular origin in healthy volunteers and patients with vestibular disorders.

METHODS

Twelve healthy volunteers (10 men and two women, aged 23-37 years) and 12 patients with vestibular disorders (6 men and 6 women, aged 29-71 years) were enrolled in this study. To record responses, surface electrodes were placed on the ipsilateral mastoid and the vertex. An electrode on the nasion served as the ground. Recording was performed using an auditory evoked potential recording system with a mini-mixer and a stereo-amplifier. Signals at the vertex to the ispilateral mastoid were amplified and bandpass filtered (100-3000 Hz). One thousand-hertz short tone bursts (1 kHz STB; rise/fall time=0.5 ms, plateau time=1 ms) were presented to either ear through a headphone with or without white noise (WN) ipsilateral to the stimulated ear. The stimulation rate was 10 Hz, and the analysis time was 10 ms. The responses to 500 stimuli were averaged twice.

RESULTS

When 1 kHz STB (95 dBnHL, equivalent to 130 dBSPL) were presented with 100 dBSPL WN (ipsilateral to the stimulated ear), a negative peak with 3-4 ms latency (N3) was observed in 23 of the 24 ears (95.8%) with reproducibility in healthy subjects. Without WN, N3 was observed in 17 of the 24 ears (70.8%). The threshold of N3 was 90.2 dBnHL on the average. The presence of N3 in the patients was in agreement with the presence of the VEMP, which were also recorded.

CONCLUSIONS

Using techniques of WN exposure ipsilateral to the stimulated ear, we recorded N3 in healthy subjects and in vestibular disorder patients with preserved hearing. This negative peak is likely to be of vestibular origin.

SIGNIFICANCE

N3 may be measured from subjects who cannot contract neck muscles due to their ages, mental states, or consciousness disorders. In other words, N3 may be measured from subjects from whom VEMP cannot be recorded. In combination with VEMP, N3 may be useful for the detection of lesion sites.

Sound-evoked myogenic potentials and responses with 3-ms latency in auditory brainstem response

OBJECTIVES

The vestibular-evoked myogenic potential (VEMP) has shed new light on vestibular testing. A large negative deflection with a 3-ms latency within the auditory brainstem response (ABR) has been reported in some patients with deafness. This negative deflection has been termed the N3 potential and it is assumed to be a vestibular-evoked potential. This study investigated the relationship between the VEMP and the N3 potential.

STUDY DESIGN

Prospective evaluation of the VEMP and the N3 potential in 21 patients.

METHODS

The oto-neurological tests, including caloric test, hearing sensitivity test, VEMP, and ABR, were performed and data were analyzed.

RESULTS

The average hearing threshold ranged from 65 to above 110 dB, which includes 9 (37.5%) totally deaf ears. The N3 potentials were recorded in 10 (41.7%) ears. A normal VEMP was detected in 16 (66.7%) ears. Canal paresis was observed in 11 (45.8%) ears.

CONCLUSIONS

Both the VEMP and the N3 potential appear to originate from the sacculus, but because the characteristics of these two responses are not identical, additional factors might be involved in the generation of the N3 potential.