Parallel auditory vestibular evoked neurogenic and myogenic potential results in a case of peripheral vestibular dysfunction, showing that the former originates from the vestibular system

PURPOSE: Vestibular evoked myogenic potentials (VEMPs) uses high intensity clicks with recording from the tonically active sternocleidomastoid muscle, taking advantage of the close proximity of the saccule to the oval window. Our group has used the same stimulus to record Vestibular Evoked Neurogenic Potentials (VENPs) directly from the brain. VEMPs are now regarded the electrophysiological gold standard in peripheral vestibular system examination. We present a case of peripheral vestibular dysfunction to show that both VEMPs and VENPs provide similar results during recovery. METHODS: A case of Meniere's Disease in recovery is examined. VEMPs were recorded using a 105 dB nHL click stimulus from the ipsilateral sternocleidomastoid muscle. VENPs were recorded using an ipsilateral parietal to Fpz montage and a 1 kHz tone-pip stimulus. Standard BAEPs and threshold latency series (TLS) were performed. RESULTS: VEMP and VENP were unobtainable from the left side at initial presentation in a patient with Meniere's Disease, with normal BAEP and TLS bilaterally. After one month of therapy both the VEMP and VENP normalized. CONCLUSIONS: As VEMPs are known to originate from the vestibular system, the parallel VENP result suggests the same for the latter VENP may prove to be useful and complement VEMP in determining vestibular dysfunction.     

糖尿病大鼠的脑干听觉诱发电位和中潜伏期反应

应用计算机平均叠加技术颅表记录大鼠脑干听觉诱发电位(BAEP)和中潜伏期反应(MLR),在链尿佐菌素(STZ)诱导的糖尿病大鼠连续70天同时动态观察BAEP和MLR的波峰潜伏期(PL)、波峰间潜伏期(IPL)及波幅的变化,旨在探讨糖尿病MLR和BAEP是否都有异常改变及同病程的关系。结果如下：糖尿病大鼠BAEP各波PL和I波-V波IPL在病程第28～42天出现持续性的明显延长,且均与病程呈正的直线相关关系;MLR各波PL和Pa波-Pb波IPL在病程第28～42天也出现持续性的明显延长,Na、Nb和Pb波PL也同病程呈正的直线相关关系。糖尿病大鼠BAEP各波波幅在病程第14～28天出现明显增大,MLR的Pa、Nb波波幅在病程第14天也出现明显增大。表明糖尿病大鼠BAEP和MLR有相似的异常改变并与病程有关。     

Source estimation of spontaneous MEG activity and auditory evoked responses in normal subjects during sleep

Summary This study focuses on source estimation of spontaneous MEG activity and auditory evoked responses during sleep. Sources of K-complexes and auditory evoked responses were investigated by magnetoencephalograph (MEG) and electroencephalograph (EEG) measurements, simultaneously. Sources of K-complexes during stage 2 sleep were investigated. The MEG results suggested that the sources of K-complexes can be modeled by two current dipoles. Dipoles for the K-complexes were estimated to be located 5 mm away from the sources of the N100 components of auditory evoked responses during wakefulness. Sources of auditory evoked responses during each sleep stage were also investigated to clarify the origins of the K-complex, the vertex sharp transient, and delta waves. Estimated dipoles for the N100 component for each sleep stage were estimated to be at slightly different locations in the auditory area. Based upon results of the MEG measurements and the EEG topographies, sources of the N330 component can be modeled by multiple current dipoles, which are seen to be distributed diffusely throughout the cerebral cortex.This work was supported in part by the grant 03505002, from the Ministry of Education Science and Culture, Japan.     

Structure of the auditory evoked magnetic fields during sleep.

We studied the effects of sleep on auditory evoked magnetic fields following pure tone stimulation applied to the right ear of 10 healthy normal volunteers to investigate the changes in the processing of auditory perception in the primary auditory cortex. Dual 37-channel biomagnetometers were used to record auditory evoked magnetic fields over the bilateral temporal lobes in response to presented tones. Auditory evoked magnetic fields were compared for three stimulus frequencies (250, 1000 and 4000 Hz) and three sleep stages (awake state, sleep stages 1 and 2). Four main components, M50, M100, M150 and M200, were identified with latencies of approximately 50, 100, 150 and 200 ms, respectively. The latency of each component had a tendency to be prolonged with the depth of sleep stage in all frequencies. The amplitude ratios of the early-latency components (M50 and M100) showed a tendency of reduction compared with the same components in the awake state. By contrast, the amplitude ratios of the long-latency components (M150 and M200) were significantly enhanced with an increase in the sleep stage compared with the same components in the awake state. The equivalent current dipoles of all components in all conditions were detected at the superior temporal cortex (the primary auditory cortex). As for the changes in the equivalent current dipole location of each component, the equivalent current dipole was detected in the more posterior and medial region in responses to the high-frequency tone (1000 and 4000 Hz) compared with those to 250 Hz tone stimulation. Although the equivalent current dipoles of the early-latency components (M50 and M100) were in regions more anterior and superior compared to those in the awake state, there was no consistent tendency of changes in equivalent current dipole locations between each sleep stage in the late-latency components (M150 and M200). These findings are probably due to the difference in generating mechanisms between the early- and late-latency components.     

The effects of alcoholism on auditory evoked potentials during sleep

Normal aging is associated with a reduction in the probability that an auditory stimulus will evoke a K-complex during sleep. Additional concomitants of aging are a reduction in the amplitude of the K-complex-related N550, an augmentation of the P2 component and the appearance of a long-lasting positivity (LLP) in the auditory evoked potential. Normal aging is also associated with a dramatic reduction in slow wave sleep (SWS) and a reduction in the volume of cortical gray matter, particularly in the frontal and prefrontal regions of the brain. As in aging, alcoholism is associated with reductions in both cortical gray matter and SWS. It can, therefore, be hypothesized that alcoholics would show similar evoked potential changes to those seen in aging. To test this hypothesis, we studied seven middle-aged abstinent long-term alcoholics and eight age-matched normal controls. Each subject spent one night in the laboratory. Electroencephalogram (EEG) was recorded from six midline scalp sites and auditory stimuli were presented during stage 2 non-rapid eye movement sleep. N550 amplitude in the K-complex average was lower in the alcoholics as compared with controls as was the likelihood of K-complex production. No differences were noted in either amplitude or latency of the P2 or N350 components, and both groups displayed a prominent LLP potential. The pattern of reduced K-complex production and N550 amplitude in alcoholics as compared with age-matched controls is consistent with an hypothesized association between atrophy of the frontal lobes and reductions in SWS and K-complexes. The finding also suggests that the evoked K-complex may be a relatively simple measure of the effect of alcoholism on EEG during sleep.     

Asymmetrical auditory probe evoked potentials during REM and NREM sleep

Two experiments were conducted to evaluate interhemispheric differences in late auditory evoked potentials (AEPs) during rapid-eye-movement (REM), Stage 2, and Stage 4 sleep. In the first study, 1,000-Hz stimuli [80 db (SPL)] were presented binaurally at a rate of 1/1.1 s. Analyses of variance were computed on the absolute difference in the amplitude of right and left evoked responses. N1 AEPs were significantly more asymmetrical in Stage 4 sleep compared to either REM or Stage 2 sleep. A second study was conducted with a wider topographical electrode distribution. This study used both a long and a short interstimulus interval with 500-Hz 80-db SPL tone pips. The absolute difference in the amplitude of right and left AEPs was compared across sleep stage. Asymmetries were larger in Stage 4 sleep than in either REM or Stage 2. Examination of these data indicated relative hemispheric balance in REM and Stage 2 sleep with largest asymmetries in Stage 4. The results do not support the view that REM and non-REM sleep stages are associated with differential activation of the two cerebral hemispheres. Rather, they suggest that the sleep cycle is characterized by variations in the degree of asymmetry. Asymmetries in Stage 4 sleep were not consistently in favor of the left hemisphere.     

Neurogenic vestibular evoked potentials using a tone pip auditory stimulus

OBJECTIVES: To obtain neurogenic vestibular evoked potentials (NVESTEPs) with surface scalp recording using a tone pip auditory stimulus. METHODS: Fourteen neurologically normal volunteers (Age range 26-45 years, 10 females and 4 males), and two patients with sensorineural hearing loss and possible multiple sclerosis respectively, were examined. Two channel recordings were obtained, the first channel being P3 referred to Fpz, and the second channel being P4 referred to Fpz. A 1 kHz tone pip stimulus with two cycles was delivered via headphones monoaurally with contralateral masking noise. RESULTS: A consistent negative wave with a mean absolute latency of 4.72 msec was obtained, which we have named N5. 25% of the ears tested had better responses at the ipsilateral parietal electrode. In the patient with bilateral sensorineural hearing loss, NVESTEPs was present, suggesting that the NVESTEP is not a cochlear response. In the patient with possible multiple sclerosis, an abnormal NVESTEP response and a normal BAEP response were found. CONCLUSION: Use of a tone-pip rather than a click auditory stimulus allows a lower click intensity to be used in the production of NVESTEP responses, leads to a shorter testing time, and is therefore more comfortable for the patient. This study adds to our impression that the NVESTEP may be a physiological response that can be used to assess the vestibular system and is different from the BAEP response. Further testing in patients with symptoms of dizziness and with disorders specific for the vestibular nerve is required.     

Click evoked neurogenic vestibular potentials (NVESTEPs): a method of assessing the function of the vestibular system

OBJECTIVES: To obtain neurogenic vestibular evoked potentials (NVESTEPs) with surface scalp recording using high intensity auditory clicks. The same stimulus is used in myogenic vestibular evoked potentials which has been shown to evoke potentials in the vestibular division of the vestibulocochlear nerve. METHODS: A whole head recording with surface EEG electrodes was performed using high intensity clicks in one normal volunteer to determine the best recording position for vestibular evoked potentials. The results were compared to responses at moderate click intensities used for brainstem auditory evoked potentials (BAEPs). The difference in the location of the two responses on the scalp was assumed to be from the vestibular system. RESULTS: Responses specific to the high intensity clicks were best obtained in the parietal areas, with no reproducible responses obtained in the same area with moderate intensity clicks normally used in BAEPs. Recordings in neurologically normal volunteers showed a consistent response with a negative polarity at around 3 ms, which we therefore called N3. Two case studies are presented. The first case is a patient with unilateral sensorineural hearing loss with NVESTEPs present, suggesting that NVESTEPs is not a cochlear response. The second case is a patient with multiple sclerosis with demyelinating lesions in the pons and an unobtainable NVESTEP response. CONCLUSION: NVESTEPs is a possible new diagnostic technique that may be specific for the vestibular pathway. It has potential use in patients with symptoms of dizziness, subclinical symptoms in multiple sclerosis, and in disorders specific for the vestibular nerve.     

A system for recording of auditory evoked responses.

A system for recording of evoked potentials from auditory stimulation was developed. The system consists of a PC equipped with an audio bandwidth board with analog input and output channels. The sound stimulus signal is generated in the computer, D/A converted, and via audio amplifier fed to earphones on the test subject. Auditory evoked potentials in response to sound stimuli are recorded via electrodes, amplified and filtered in an EEG recording system and fed to an A/D converter. The signal is analysed in the PC. The modular design of the program makes it a flexible system where stimulus and recording parameters can easily be modified and new applications can be added to standard clinical measurements. Three applications that are not possible with commercially available systems were developed and evaluated. a) A diagnostic procedure to verify hydrops in patients with Meniere's disease. b) Intraoperative recordings of auditory evoked potentials during neurootological surgery. c) Recording of mismatch negativity (MMN) potentials in evaluation of central auditory functions.     

Suppression of the auditory middle-latency response and evoked gamma-band response in a paired-click paradigm

When two clicks are presented within 500 ms and the clicks are separated by several seconds, a typical finding is a suppression of the amplitude of the P50 component of the middle-latency auditory-evoked response. In the present study, we investigated whether only the P50 or also the earlier components Po, Na, Pa and Nb, and the exogenous components N100 and P200 exhibit an amplitude suppression to the second click. In addition, we studied the suppression behaviour of the auditory-evoked 40-Hz gamma-band response in the time and frequency domain. We found a significant amplitude suppression to the second click for all components of the auditory-evoked potential following Po, which was most pronounced at electrode Cz. When testing the successive peaks and troughs of the evoked 40-Hz gamma-band response in the time domain, we found a significant amplitude suppression for peaks and troughs with the same latency and polarity as the middle-latency components following Po, which was most pronounced at electrodes Fz and Cz. Consequently, the amplitude of the 40-Hz evoked gamma-band response in the frequency domain paralleled the findings of the time domain, with a significant amplitude suppression to the second tone, which was most pronounced at electrodes Fz and Cz. Results are discussed with reference to the early sensory-gating hypothesis.     

前庭系统性眩晕患者的脑干听觉诱发电位探讨

目的 :探讨脑干听觉诱发电位 (BAEP)与前庭周围性眩晕和中枢性眩晕的相关性。方法 :对 2 96例前庭系统性眩晕患者进行BAEP检查 ,并记录其各波潜伏期 (PL)、波峰间潜伏期 (IPL)的数值。结果 :2 96例中 ,15 1例BAEP异常 ,异常率 5 1%。其表现分为两组 :①内耳型组 6 8例 :可见I波消失或I波和其后各波均消失 ,或I波PL延长及其后各波相应延长 ,以及V波PL、I-V波IPL延长 ;②脑干型组 83例 :表现为I波正常 ,III波或V波PL延长或波形消失 ,III-V、I-III之IPL延长 ,V/I波幅比小于0 5及双侧V波PL侧间差 >0 2 6ms。结论 :内耳型组为前庭周围性眩晕 ,脑干型组则为前庭中枢性眩晕 ,BAEP表现两组不同 ,说明BAEP对鉴别前庭系统性眩晕有一定的价值。     

脑干听觉诱发电位对前庭系统性眩晕的临床诊断价值

目的：探讨脑干听觉诱发电位（BAEP）对前庭周围性眩晕和前庭中枢性眩晕的诊断价值。方法：对90例前庭系统性眩晕患者（病例组）及50例健康人（对照组）进行BAEP检测,分别观测和比较各波分化情况,I、Ⅲ、V波潜伏期（PL）,I-Ⅲ、Ⅲ-V、I—V波峰间期（IPL）,两侧耳间差（ILD）,V／I波的波幅比,并进行统计学分析。结果：健康对照组波形分化良好。病例组90例中有67例（74％）BAEP异常,主要表现为波形分化异常,PL、IPL延长,其中周围性眩晕有28例（42％）,中枢性眩晕有39例（58％）。正常对照组与病例组I、Ⅲ、V波PL及I-Ⅲ、Ⅲ一V、I—V波的IPL比较,差异均有统计学意义（P〈0．05）。结论：BAEP对前庭周围性眩晕、中枢性眩晕的诊断和鉴别诊断具有重要价值,对临床治疗及预后具有一定的指导意义。     

Imaging the dynamics of the auditory steady-state evoked response

This study used magnetoencephalography (MEG) to examine the dynamic patterns of neural activity underlying the auditory steady-state response. We examined the continuous time-series of responses to a 32-Hz amplitude modulation. Fluctuations in the amplitude of the evoked response were found to be mediated by non-linear interactions with oscillatory processes both at the same source, in the alpha and beta frequency bands, and in the opposite hemisphere.     

Topographic recordings of auditory evoked potentials to speech: Subcortical and cortical responses

Topographies of speech auditory brainstem response (speech ABR), a fine electrophysiological marker of speech encoding, have never been described. Yet, they could provide useful information to assess speech ABR generators and better characterize populations of interest (e.g., musicians, dyslexics). We present here a novel methodology of topographic speech ABR recording, using a 32‐channel low sampling rate (5 kHz) EEG system. Quality of speech ABRs obtained with this conventional multichannel EEG system were compared to that of signals simultaneously recorded with a high sampling rate (13.3 kHz) EEG system. Correlations between speech ABRs recorded with the two systems revealed highly similar signals, without any significant difference between their signal‐to‐noise ratios (SNRs). Moreover, an advanced denoising method for multichannel data (denoising source separation) significantly improved SNR and allowed topography of speech ABR to be recovered.     

Attention to external stimuli during wakefulness and sleep: evoked 40-Hz response and N350

Changes of two components of the auditory event-related potential, the evoked 40-Hz response and the N350, were studied during different stages of wakefulness and sleep. The evoked 40-Hz response has been proposed to represent an attention-modulating mechanism; the N350 seems to reflect an inhibitory process associated with reduced information processing. Because recent literature suggests that both components reflect opposite mechanisms, an inverse relationship was expected. Ten participants were presented with tone pips while reading, lying awake in bed, and during light sleep, slow wave sleep, and REM sleep. A significant evoked 40-Hz response was observed during reading and lying awake in bed. N350 was evident in all conditions and, as expected, peaked during light sleep. The hypothesized inverse relationship was confirmed. These findings support former proposals that relate both components to attention. Possibly, the N350 is most pronounced during the sleep transition period because its inhibitory processes have to prevail over the attentional mechanisms (40-Hz response) to permit sleep onset.