The Effects of Plateau Time on Vestibular-evoked Myogenic Potentials Triggered by Tone Bursts

Vestibular-evoked myogenic potentials (VEMPs) can be triggered by acoustic, vibratory or galvanic stimuli. However, each method has drawbacks for studying if the vestibulocollic reflex is intact in the patients tested. We used air-conducted VEMPs as a screening test to examine the integrity of the sacculocollic reflex. In a previous study, we defined the optimal rise fall time of short tone bursts (STBs) to evoke VEMPs. In this paper, we studied the optimal plateau time of tone bursts to evoke VEMPs. Four different plateau times (1, 2, 5 and 10 ms) were used in a random order to test 26 normal ears. VEMP responses (p13 n23) triggered by the tone bursts were clearly observed in all ears. When the plateau time was increased in order from 1 to 10 ms, the latencies (p13, n23) and interval (p13-n23) were also increased in parallel, although significant differences were not observed between some plateau times. Considering the latencies and interval together for the four plateau times, the variances were smallest for the 2 ms plateau time, meaning that it caused the smallest interaural VEMP differences. The amplitude or relative amplitude in individual ears was lowest for the 1 ms plateau time, while it was comparable for the other three plateau times. In conclusion, we recommend that the ideal stimulation pattern for evoking STB VEMPs is as follows: frequency 500 Hz; stimulation repetition rate 5 Hz; rise fall time 1 ms; and plateau time 2 ms. The waveform morphology of the VEMP responses observed with this stimulation pattern was simultaneously the most constant and marked.     

The effects of plateau time on vestibular-evoked myogenic potentials triggered by tone bursts

Vestibular-evoked myogenic potentials (VEMPs) can be triggered by acoustic, vibratory or galvanic stimuli. However, each method has drawbacks for studying if the vestibulocollic reflex is intact in the patients tested. We used air-conducted VEMPs as a screening test to examine the integrity of the sacculocollic reflex. In a previous study, we defined the optimal rise/fall time of short tone bursts (STBs) to evoke VEMPs. In this paper, we studied the optimal plateau time of tone bursts to evoke VEMPs. Four different plateau times (1, 2, 5 and 10 ms) were used in a random order to test 26 normal ears. VEMP responses (p13/n23) triggered by the tone bursts were clearly observed in all ears. When the plateau time was increased in order from 1 to 10 ms, the latencies (p13, n23) and interval (p13-n23) were also increased in parallel, although significant differences were not observed between some plateau times. Considering the latencies and interval together for the four plateau times, the variances were smallest for the 2 ms plateau time, meaning that it caused the smallest interaural VEMP differences. The amplitude or relative amplitude in individual ears was lowest for the 1 ms plateau time, while it was comparable for the other three plateau times. In conclusion, we recommend that the ideal stimulation pattern for evoking STB VEMPs is as follows: frequency 500 Hz; stimulation repetition rate 5 Hz; rise, fall time 1 ms; and plateau time 2 ms. The waveform morphology of the VEMP responses observed with this stimulation pattern was simultaneously the most constant and marked.     

Effect of click duration on vestibular-evoked myogenic potentials

CONCLUSIONS: The 0.5-VEMP demonstrated a more prominent waveform morphology than either the 0.1- or 0.2-VEMPs. In addition, the 0.5-VEMP had smaller interaural latency differences than the 1.0-VEMP. These findings suggest that 0.5 ms is superior to other click durations in terms of yielding VEMP responses for clinical use. OBJECTIVE: In order to establish the ideal stimulus condition for vestibular-evoked myogenic potentials (VEMPs), we studied the use of various click durations to generate different response patterns in normal subjects. The influence of click durations on VEMPs is described and the optimal stimulation duration for clinical use is suggested. MATERIAL AND METHODS: This was a prospective study. Eighteen healthy volunteers (36 ears) underwent VEMP tests. Four click durations (0.1, 0.2, 0.5 and 1.0 ms) were used in a random order to elicit VEMP responses (0.1-, 0.2-, 0.5- and 1.0-VEMP, respectively). The latency of each peak (p13, n23), the peak-to-peak interval and amplitude (p 13-n23) and the relative amplitude (defined as the amplitude divided by that of the 0.5-VEMP) were measured and compared. RESULTS: Click stimulation of 34 ears (94%) produced 0.1-VEMP responses, whereas positive 0.2-, 0.5- and 1.0-VEMP responses were observed in 36 (100%). The latencies of peaks p13 and n23 were significantly prolonged between successive stimulus durations from 0.1 to 1.0 ms (p <0.05), in contrast to the p13-n23 intervals (p >0.05). The 1.0-VEMP displayed the largest SDs of latencies and interval among the four different VEMPs. The relative amplitude was significantly increased between successive durations from 0.1 to 0.5 ms (alphaT <0.05), but there was no significant difference between 0.5 and 1.0 ms (alphaT >0.05).     

The effect of rise/fall time on vestibular-evoked myogenic potential triggered by short tone bursts.

Vestibular-evoked myogenic potentials (VEMPs) are used more and more frequently as a clinical tool to test if the sacculocollic reflexes are intact in patients. They can be evoked by short tone bursts (STBs) as well as by clicks. Although most previous studies used traditional clicks to generate VEMP responses, our clinical experience showed that STBs were prone to evoke them more clearly, at least in some patients. Four kinds of STB stimulation patterns in a random order were used to test 22 ears using changing rise/fall times (0.3, 1, 3 and 10 ms). VEMP responses (p13/n23) triggered by these patterns were clearly observed in all 22 ears. When the rise/fall time was prolonged from 0.3 to 10 ms, the p13 latency was prolonged in parallel. There was a similar trend for the n23 latency, although a significant difference was not attained between 0.3 ms and 1 ms rise/fall times. Considering the p13 and n23 latencies for the 4 rise/fall times, the variances were smallest for the 1 ms stimulation, meaning that it caused the smallest interaural latency differences. The amplitude or relative amplitude in the individual ears tested was lowest for the 10 ms stimulation, being comparable among the other 3 rise/fall times. In conclusion, the 1 ms rise/fall time was a remarkable stimulation pattern because its VEMP responses were simultaneously more constant and conspicuous.     

The Effect of Rise/Fall Time on Vestibular-evoked Myogenic Potential Triggered by Short Tone Bursts

Vestibular-evoked myogenic potentials (VEMPs) are used more and more frequently as a clinical tool to test if the sacculocollic reflexes are intact in patients. They can be evoked by short tone bursts (STBs) as well as by clicks. Although most previous studies used traditional clicks to generate VEMP responses, our clinical experience showed that STBs were prone to evoke them more clearly, at least in some patients. Four kinds of STB stimulation patterns in a random order were used to test 22 ears using changing rise/fall times (0.3, 1, 3 and 10 ms). VEMP responses (p13/n23) triggered by these patterns were clearly observed in all 22 ears. When the rise/fall time was prolonged from 0.3 to 10 ms, the p13 latency was prolonged in parallel. There was a similar trend for the n23 latency, although a significant difference was not attained between 0.3 ms and 1 ms rise/fall times. Considering the p13 and n23 latencies for the 4 rise/fall times, the variances were smallest for the 1 ms stimulation, meaning that it caused the smallest interaural latency differences. The amplitude or relative amplitude in the individual ears tested was lowest for the 10 ms stimulation, being comparable among the other 3 rise/fall times. In conclusion, the 1 ms rise/fall time was a remarkable stimulation pattern because its VEMP responses were simultaneously more constant and conspicuous.     

Comparison of tone burst and tapping evocation of myogenic potentials in patients with chronic otitis media

OBJECTIVE: Vestibular evoked myogenic potential (VEMP) has recently been broadly studied in cochleo-vestibular disorders to elucidate its mechanism. Because it is evoked by loud sound stimulation, impairment of the sound transmission through the middle ear may affect VEMP results. This study aims to compare the response rate of VEMPs using the tone burst method and the tapping method in patients with chronic otitis media (COM). DESIGN: Fourteen patients (22 ears) with conductive hearing loss due to COM were subjected to VEMP tests using both the tone burst method and the tapping method. Each ear was stimulated by a short-tone burst (95 dB nHL, 500 Hz), followed by tapping on the forehead with a tendon hammer, 200 times at a frequency of 5 Hz. RESULTS: Thirteen (59%) of the 22 ears showed positive VEMPs using the tone burst method, whereas 20 ears (91%) displayed positive VEMPs by the tapping method (p < 0.05). The latencies of wave p13 and n23, and the amplitude p13-n23 using the tone burst method were 13.4 +/- 4.1 msec, 20.5 +/- 4.6 msec, and 77.2 +/- 17.2 microV, respectively. These results do not significantly differ from those obtained using the tapping method. In ears with perforated eardrums (N = 11), five ears (45%) displayed positive VEMPs by the tone burst method; compared with nine ears (82%) with positive VEMPs using the tapping method, representing a nonsignificant difference. In ears with healed eardrums (N = 11), eight ears exhibited positive VEMPs by tone burst, with a mean air-bone gap of 25.6 +/- 15.2 dB at 500 Hz, in contrast to a gap of 30.0 +/- 22.9 dB in three ears without VEMPs, indicating no significant difference. CONCLUSIONS: When stimulating sound is attenuated by middle ear pathology, VEMPs are expected to be poorly elicited. Under such conditions, myogenic potentials may be evoked with the tapping method to elicit the absent VEMPs that result from middle ear or inner ear pathology.     

Comparison of the diagnostic value of 3 T MRI after intratympanic injection of GBCA, electrocochleography, and the glycerol test in patients with Meniere's disease

Conclusions The 0.5-VEMP demonstrated a more prominent waveform morphology than either the 0.1- or 0.2-VEMPs. In addition, the 0.5-VEMP had smaller interaural latency differences than the 1.0-VEMP. These findings suggest that 0.5 ms is superior to other click durations in terms of yielding VEMP responses for clinical use.

Objective In order to establish the ideal stimulus condition for vestibular-evoked myogenic potentials (VEMPs), we studied the use of various click durations to generate different response patterns in normal subjects. The influence of click durations on VEMPs is described and the optimal stimulation duration for clinical use is suggested.

Material and methods This was a prospective study. Eighteen healthy volunteers (36 ears) underwent VEMP tests. Four click durations (0.1, 0.2, 0.5 and 1.0 ms) were used in a random order to elicit VEMP responses (0.1-, 0.2-, 0.5- and 1.0-VEMP, respectively). The latency of each peak (p13, n23), the peak-to-peak interval and amplitude (p13-n23) and the relative amplitude (defined as the amplitude divided by that of the 0.5-VEMP) were measured and compared.

Results Click stimulation of 34 ears (94%) produced 0.1-VEMP responses, whereas positive 0.2-, 0.5- and 1.0-VEMP responses were observed in 36 (100%). The latencies of peaks p13 and n23 were significantly prolonged between successive stimulus durations from 0.1 to 1.0 ms (p<0.05), in contrast to the p13-n23 intervals (p>0.05). The 1.0-VEMP displayed the largest SDs of latencies and interval among the four different VEMPs. The relative amplitude was significantly increased between successive durations from 0.1 to 0.5 ms (α_T<0.05), but there was no significant difference between 0.5 and 1.0 ms (α_T>0.05).     

Vestibular evoked myogenic potentials in newborns

This study presents a novel method for recording vestibular evoked myogenic potential (VEMP) in newborns, used to investigate the maturation of sacculocollic reflex at birth.Twenty full-term newborns aged 2-5 days old were enrolled in this study. During natural sleep, each newborn underwent distortion product otoacoustic emission test, and VEMP test using the head rotation method. For comparison, 20 healthy adults also underwent VEMP test using the same method. Based on adult criteria, 40 newborn ears revealed normal VEMPs in 40%, prolonged VEMPs in 35%, and absent VEMPs in 25%, indicating that great variation exists in the maturation of the sacculocollic reflex at birth. Comparison of VEMP characteristics between healthy newborns and adults revealed nonsignificant difference in the response rate and the latency of n23. However, significant differences existed in the latency of p13, interpeak p13-n23 interval and p13-n23 amplitude between newborns and adults. In conclusion, VEMPs in newborns can be easily recorded by the head rotation method. Prolonged or absent VEMPs in newborns may reflect incomplete maturity of the sacculocollic reflex pathway, especially the myelination. A further large number of newborns receiving MRI scan for other reasons may undergo VEMP test to verify this hypothesis.     

骨导振动刺激诱发的前庭诱发肌源性电位

目的探讨B81骨振子在前庭诱发肌源性电位(vestibular evoked myogenic potentials, VEMPs)检测中的应用。方法对25例正常志愿者的双耳行插入式气导声刺激(air conducted sound, ACS),单侧乳突B81骨导振动刺激(bone conducted vibration, BCV)的VEMPs检查,并对ACS ,BCV VEMPs检查结果进行统计学分析。结果ACS ,BCV 眼肌前庭诱发肌源性电位(ocular vestibular evoked myogenic potentials, oVEMP)的引出率分别为92%（46/50）,98%（49/50）。BCV oVEMP与ACS oVEMP比较,两者引出率差异无统计学意义（P=0.36）;两者N1波潜伏期（P=0.00）、P1波潜伏期（P=0.00）、N1 P1波间期(P=0.01)及振幅(P=0.00)差异均具有统计学意义（P<0.05）;BCV oVEMP的N1、P1波潜伏期,N1 P1波间期均较短,而振幅较大。ACS ,BCV 颈肌前庭诱发肌源性电位(cervical vestibular evoked myogenic potential, cVEMP)的引出率均为100%（50/50）。BCV cVEMP与ACS cVEMP比较,N1波潜伏期差异无统计学意义（P=0.96）,P1波潜伏期（P=0.02）,P1 N1波间期(P=0.00)、振幅(P=0.04)均有统计学差异（P＜0.05）;BCV cVEMP的P1波潜伏期较短,P1 N1波间期较长,振幅较大。BCV oVEMP、ACS oVEMP、BCV cVEMP和ACS cVEMP的两耳间振幅不对称率（%）分别为：28.08±21.10、27.95±18.13、23.60±17.86、32.24±18.92。结论B81骨振子可以用于VEMPs的检测,骨导振动刺激在评价传导性听力损失患者的前庭耳石器功能时优于气导声刺激,可作为气导声刺激诱发VEMPs的补充检查。     

Vestibular evoked myogenic potentials are intact after sudden deafness

OBJECTIVE: To evaluate vestibular evoked myogenic potentials (VEMPs) in cases of sudden deafness, and to confirm the noncochlear origin of the VEMPs. STUDY DESIGN: Prospective study. VEMPs, which were evoked by short tone burst (95 dB nHL) stimulation, were recorded in 20 patients with unilateral, idiopathic sudden deafness. The results of the deaf ears were compared with those of the contralateral healthy ears and the normal control ears. The relations between VEMPs and the hearing level or caloric response were then investigated. RESULTS: All 20 of the deaf ears displayed normal biphasic VEMPs. The mean latencies of p13 and n23, as well as mean amplitude p13-n23, were 15.1 +/- 2.8 msec, 20.7 +/- 3.3 msec and 25.2 +/- 12.6 microV, respectively, not significantly different to either the contralateral healthy ears (p > 0.05) or the normal control ears (p > 0.05). Five deaf ears displayed canal paresis or absent caloric response, whereas the remaining 15 ears revealed normal caloric response. CONCLUSION: All the lesioned ears of patients with idiopathic sudden deafness exhibit normal biphasic VEMPs. Neither the hearing level nor the caloric response correlated to the VEMPs.     

Properties of binaural vestibular evoked myogenic potentials elicited with air-conducted and bone-conducted tone bursts

The purpose of this investigation was to compare the effects of monaural and binaural stimulation on unilaterally-measured vestibular evoked myogenic potential (VEMP) magnitude and latency. The subjects were eighteen normal-hearing adults with no history of vestibular disease. Monaural VEMPs were acquired with air-conducted (AC) and bone-conducted (BC) 500 Hz tone bursts presented at 95 dB nHL and 70 dB nHL, respectively. These stimuli were simultaneously paired with 95 dB nHL contralateral tone bursts at 250, 500, 750, or 1000 Hz during acquisition of binaural VEMPs. Results indicated that AC-VEMP relative magnitudes decreased in each of the binaural conditions compared to the monaural condition. However, no changes in relative magnitude between conditions occurred for BC-VEMPs. Similar latencies were observed for monaural and binaural VEMPs. Differences in bilateral interaction seen between the AC-VEMP and BC-VEMP conditions are consistent with modification of sound transmission through the ear during presentations of binaural sound.     

听力正常儿童骨导前庭诱发肌源性电位正常值的建立

目的 记录听力正常儿童骨导前庭诱发肌源性电位(BC-VEMP)特征,为临床儿童前庭功能评估提供参考。 方法 选择31名(62耳)4~12岁听力正常儿童,按照年龄进行分组,4~5岁组11人(22耳),6~12岁组20人(40耳),行BC-VEMP测试。将60 dB nHL作为起始刺激强度,记录骨导刺激时颈性VEMP(cVEMP )、眼性VEMP(oVEMP)的N1潜伏期、P1潜伏期、N1-P1波间期、N1-P1波幅、波幅不对称比以及阈值。使用SPSS软件进行统计学分析。 结果 4~12岁听力正常儿童BC-VEMPs引出率为100%。4~5岁组与6~12岁组相比,BC-cVEMP的P1、N1潜伏期、P1-N1波间期、P1-N1波幅、阈值、波幅不对称比均无统计学差异(P>0.05)。两组间BC-oVEMP的N1、P1潜伏期、N1-P1波间期、N1-P1波幅、阈值、波幅不对称比均无统计学差异(P>0.05)。 结论 BC-VEMPs是一种可行的前庭功能辅助性检査手段,不同年龄段儿童BC-VEMPs正常值的建立,可为儿童前庭功能的评估提供参考。     

Properties of binaural vestibular evoked myogenic potentials elicited with air-conducted and bone-conducted tone bursts

The purpose of this investigation was to compare the effects of monaural and binaural stimulation on unilaterally-measured vestibular evoked myogenic potential (VEMP) magnitude and latency. The subjects were eighteen normal-hearing adults with no history of vestibular disease. Monaural VEMPs were acquired with air-conducted (AC) and bone-conducted (BC) 500 Hz tone bursts presented at 95 dB nHL and 70 dB nHL, respectively. These stimuli were simultaneously paired with 95 dB nHL contralateral tone bursts at 250, 500, 750, or 1000 Hz during acquisition of binaural VEMPs. Results indicated that AC-VEMP relative magnitudes decreased in each of the binaural conditions compared to the monaural condition. However, no changes in relative magnitude between conditions occurred for BC-VEMPs. Similar latencies were observed for monaural and binaural VEMPs. Differences in bilateral interaction seen between the AC-VEMP and BC-VEMP conditions are consistent with modification of sound transmission through the ear during presentations of binaural sound.     

Effect of head position on vestibular evoked myogenic potentials with toneburst stimuli

CONCLUSION: The present study demonstrated the robustness of VEMP testing with toneburst stimuli, since it is hardly affected by head position, i.e. base or tonic excitation levels of the saccule and inferior vestibular nerve. However, the small but highly significant difference found in latency should not be neglected: the gravitational axis in the upright position may have some special effect on tonic excitation of the saccule. OBJECTIVES: To evaluate the effect of head positions on vestibular evoked myogenic potentials (VEMPs) with toneburst stimuli. MATERIALS AND METHODS: VEMPs were recorded with short tonebursts of 500 Hz in 14 normal subjects in 5 head positions (upright, nose up, ear up, nose down, and ear down). The three parameters analyzed were: 1) latency of p13, 2) latency of n23, and 3) corrected amplitude of p13-n23 (CA p13-n23). RESULTS: One-way repeated measures ANOVA showed significant effects on both p13 (p=0.0245) and n23 (p<0.0001) latencies, but not on CA p13-n23. Bonferroni's post hoc test demonstrated that there were significant differences in n23 latency between the upright position and all other head positions leaning on the bed.     

Vestibular evoked myogenic potentials in delayed endolymphatic hydrops

OBJECTIVE/HYPOTHESIS: Vestibular evoked myogenic potential (VEMP) has become an established test to explore the sacculo-collic reflex. The study aims to investigate the VEMPs in cases of delayed endolymphatic hydrops because greatly dilated saccule was observed in histopathological specimens of delayed endolymphatic hydrops. STUDY DESIGN: Prospective study. METHODS: Twenty patients with delayed endolymphatic hydrops were subjected to pure-tone audiometry, caloric testing, and VEMP test. Delayed VEMP was defined as the latency of peak I exceeding 22.6 milliseconds or of peak II exceeding 33.1 milliseconds. Interaural amplitude difference over the sum of amplitudes of both ears was measured, and when the ratio exceeded 0.36, it was identified as augmented VEMP or depressed VEMP depending on whether the amplitude of the lesioned side was greater or less than the opposite side. RESULTS: The VEMP test revealed that 9 patients (45%) were normal, 6 (30%) exhibited absent VEMPs, and 5 (25%) displayed abnormal VEMPs, including delayed VEMPs in 2, depressed VEMPs in 2, and augmented VEMPs in 1. The caloric test indicated that 9 (47%) of the 19 ears exhibited normal caloric response, whereas 10 ears displayed abnormal caloric responses including canal paresis in 8 and absent caloric response in 2. Six ears had preserved both the caloric response and the VEMPs, whereas no ear demonstrated both absent caloric response and absent VEMPs. CONCLUSIONS: The residual caloric as well as saccular functions after ear insult may determine whether delayed endolymphatic hydrops will occur. These findings suggest that patients with sudden deafness or juvenile unilateral total deafness should undergo caloric testing and VEMP test to predict the occurrence of delayed endolymphatic hydrops in the future.     

Eliciting constant and prominent waves n34-p44 of vestibular-evoked myogenic potentials

OBJECTIVE: The serial peaks of vestibular-evoked myogenic potentials (VEMPs) have been labeled p13, n23, n34 and p44 according to their latency. Waves p13-n23 have been shown to be of saccular origin, whereas the origin of waves n34-p44 is still unknown. In order to improve the clinical applicability of waves n34-p44, we examine the use of different patterns of acoustic stimuli to evoke constant and prominent VEMPs, especially waves n34-p44. MATERIAL AND METHODS: In this prospective study 27 healthy volunteers (54 ears) underwent VEMP tests. Three kinds of click intensity (85, 95 and 105 dB nHL) were presented in a random order to evoke 85-VEMP, 95-VEMP and 105-VEMP, respectively. The response rate, latency of each peak, peak-to-peak interval and amplitude of waves p13-n23 and n34-p44 were measured and analyzed. RESULTS: The response rates of waves p13-n23 in 85-VEMP, 95-VEMP and 105-VEMP were 26% (14/54), 89% (48/54) and 98% (53/54), respectively. Significant differences in the response rate existed between 85-VEMP and both 95-VEMP and 105-VEMP (p<0.01), whereas there was a non-significant difference between 95-VEMP and 105-VEMP (p>0.05). In contrast, the response rates for eliciting waves n34-p44 were 19% (10/54), 63% (34/54) and 89% (48/54), using 85, 95 and 105 dB acoustic stimuli, respectively. A significantly higher response rate for waves n34-p44 occurred when the intensity of the stimuli increased (p<0.01). Although neither latencies nor interval exhibited a significant difference between 95-VEMP and 105-VEMP, the amplitude of 105-VEMP was significantly greater than that of 95-VEMP for both waves p13-n23 and n34-p44. CONCLUSION: An acoustic stimulus intensity of 105 dB nHL is required to reliably elicit waves n34-p44 in subjects with normal hearing.     

VEMP responses are not affected in non-insulin-dependent diabetes mellitus patients with or without polyneuropathy

CONCLUSION: Vestibular evoked myogenic responses (VEMPs) are not affected in non-insulin-dependent diabetes mellitus (NIDDM) patients with or without polyneuropathy. OBJECTIVE: To compare VEMP responses of NIDDM patients and healthy subjects. SUBJECTS AND METHODS: VEMP responses were collected from 25 NIDDM patients with polyneuropathy (PNP), 13 NIDDM patients without PNP and 21 healthy subjects using click stimulation. After excluding ears with hearing loss (HL) (worse than 25 dB) the VEMP responses (p13 and n21 latencies and amplitude) recorded in 105 dB stimulus intensity were compared. RESULTS: There was no statistically significant difference between groups. VEMP responses were found to be normal in NIDDM patients with or without PNP.     

Effect of white noise on vestibular evoked myogenic potentials

OBJECTIVES: To clarify if p13-n23 of vestibular evoked myogenic potentials (VEMPs) is independent of cochlear afferents. METHODS: Twenty normal volunteers and 10 patients with hemifacial palsy enrolled into this study. VEMP and auditory brainstem responses (ABRs) were recorded with or without white noise (WN, 75 dBnHL or 95 dBnHL) ipsilaterally or contralaterally to the stimulated ear. Short tone bursts (STBs) of 0.5 kHz (95 dBnHL, rise/fall time=1 ms, plateau time=2 ms) were presented though headphones. For recording VEMPs surface electromyographic activity was recorded in the supine subjects form symmetrical sites over the upper half of each SCM with a reference electrode over the upper sternum. RESULTS: The amplitude of p13-n23 significantly decreased during exposure of the contralateral ear as well as the ipsilateral ear to 95 dBnHL WN in normal volunteers (41% reduction by the ipsilateral exposure and 38% reduction by the contralateral exposure). Exposure to 75 dBnHL WN caused only minimal reduction of the amplitudes of p13-n23 (5% reduction) although it caused remarkable reduction of the amplitudes of V-SN(10) (ABRs) (23% reduction). However, 95 dBnHL WN exposure showed no effect on the amplitudes of p13-n23 in the ipsilateral side to hemifacial palsy. CONCLUSION: Overall the data are in favor of the hypothesis that cochlear afferents could affect the amplitude of p13-n23 only through the stapedial reflex, although our data might not be strict proof of an absence of influence of cochlear afferents' activity.     

人工耳蜗植入术后患者前庭诱发肌源性电位的研究

目的探讨人工耳蜗植入术对患者前庭功能的影响。方法本研究入选对象为2001年至2009年由同一术者行人工耳蜗植入手术,且均为术后6个月以上年龄大于6岁的患者。排除1例非前庭因素自行放弃使用人工耳蜗者,共有12例患者参与本研究。应用前庭诱发肌源性电位（vestibular evoked myogenic potential,VEMP）检查进行前庭功能检测,以p13、n23波潜伏期与振幅作为评定指标。结果12例患者双侧短声刺激p13波和n23波出现率为50%（6/12）。诱发出波形的手术耳组p13潜伏期与非手术耳组相比,两者无显著性差异（P＞0.05）。手术耳组n23潜伏期与非手术耳组相比,两者无显著性差异（P＞0.05）。|p13-n23|手术耳组与非手术耳组相比,两者无显著性差异（t=0.009,P＞0.05）。手术耳组振幅低于非手术耳组振幅,差异具有统计学意义（t=3.75,P<0.05）。结论人工耳蜗植入术对VEMP的传导并无影响,但可造成手术耳VEMP振幅下降,可能与人工耳蜗植入术的手术刺激或长期的电极植入对球囊功能的影响有关。     

人类声诱发短潜伏期负电位的研究

目的在极重度感音性聋耳的ABR检测中发现一个位于3～4ms潜伏期的"V"字形负向波形,称声诱发短潜伏期负电位(Acoustically Evoked Short Latency Negative Response,ASNR)。本研究通过大宗病例调查和临床实验来探讨ASNR的特点和起源。方法回顾性调查并分析3104例ABR检测结果,以详尽了解ASNR的出现率和特性。对20名双耳极重度感音性耳聋患者(6～62岁)和12名健康人(23～30岁)进行了ABR和前庭诱发肌源性电位(VEMP)测试。患者组包括了16名人工耳蜗植入术后的患者,植入耳在裸耳状态时可提供无功能耳蜗模型。结果判读侧重于:人工耳蜗植入耳能否诱发ASNR,以及对比在极重度感音性聋耳中ASNR组和非ASNR组的VEMP出现率及反应阈值。结果ASNR仅出现于极重度感音性聋耳,并且对强声刺激(80～120dBnHL)有依赖性。在653例极重度感音性聋患者(981耳)的ABR波形中,有80例(12.3%)117耳(11.9%)出现了ASNR。ASNR有良好的重复性,可排除伪迹干扰的可能性。ASNR具有神经电位的特征,表现在随着声刺激的增强,其潜伏期缩短而振幅增大。ASNR与ABR的波形完全不一样,无法将其解释为传统听觉神经通路产生的电位。临床实验中,3个人工耳蜗植入耳能诱发出ASNR,说明ASNR的发生与耳蜗无关。所有9个ASNR耳都诱发出VEMP,且阈值与正常对照组无统计学差异(P>0.05),提示ASNR耳具有正常的球囊功能。在非ASNR组中,三分之二没有引出VEMP,而另外三分之一虽然可以诱发出VEMP,但阈值明显较正常对照组高(P<0.01),分别提示球囊功能丧失或低下。此外,有一外半规管麻痹耳诱发出了ASNR和VEMP。结论ASNR并非伪迹,而是一种依赖强声刺激,且只出现于极重度感音性聋耳的神经电位。ASNR的出现完全依赖于正常的球囊功能,而不依赖于残余听力或者半规管功能。据此认为ASNR起源感觉器官为球囊,根据其潜伏期推测电位源自前庭神经核。