Methods for determining auditory evoked brain-stem response thresholds in human newborns

Previous investigators have reported that newborn auditory evoked brain-stem responses (ABRs) are 20-30 dB higher than adult psychophysical thresholds to the same stimuli. These investigators reduced the intensity of the stimulus until they no longer reported an ABR to the stimulus. We adapted 2 widely used psychophysical methods, the up-down-transformed response (UDTR) method and the method of constant stimuli, for ABR threshold determination of human newborns. Response judgments were made blindly. ABR thresholds of healthy normal newborns by both procedures were no more than 10-15 dB higher than adult psychophysical thresholds. The differences between the newborn ABR thresholds we reported and those in the literature were probably explained by different procedures including the method used to estimate adult psychophysical thresholds. The correlations between ABR thresholds and suprathreshold ABR latencies and amplitudes and latency and amplitude/intensity functions were modest at best. In normal newborns suprathreshold ABR measurements are of little value in predicting ABR thresholds.     

Reproducibility of auditory brain-stem evoked responses as a function of the stimulus, scorer and subject

The reproducibility of auditory brain-stem evoked response (ABR) measurements was determined in a series of studies. ABRs were recorded from pre-term (32 and 36 weeks) newborns, term newborns, and adults to 3 different stimuli. Records were scored blindly with no knowledge of the subject, stimulus eliciting the response, or other records by that subject. Two scorers (inter-scorer reliability) and a single scorer over time (intra-scorer reliability) could score records using explicit criteria with a high degree of agreement. In contrast variability between replicate records to the same stimulus from the same subject was considerable. Intra-subject variability was not strongly affected by the age of the subject but was a function of the eliciting stimulus (the low intensity and fast repetition rate stimuli elicited more variable responses than loud, slow stimuli) and the wave measured (wave I latency was significantly more variable than the other measurements). Healthy, term newborns were studied to investigate the reproducibility of ABRs in the first few days after birth. There was a rapid reduction in ABR latency in the first 6-12 h after birth and a more gradual reduction thereafter. The prolonged latencies observed immediately after birth were associated with an elevation in ABR threshold. The reduction in latency was observed in vaginal and cesarean deliveries. These same effects were observed for amplitude of the ABR, but the trends were generally not significant. Despite the large changes in ABR latency within the first few days after birth, ABR latencies in response to some stimuli were significantly correlated between sessions separated by all intervals tested, ranging from 2 h to 2 days.     

Effects of pentylenetetrazole and 4-aminopyridine on the auditory brainstem response (ABR) and on the hearing sensitivity in the guinea pig in vivo

For exploring a possible connection between the reduced hearing sensitivity and certain abnormalities in the auditory brainstem responses (ABRs) in generalized epilepsy, the effects of two convulsing agents, namely pentylenetetrazole (PTZ) and of 4-aminopyridine (4-AP), on: (1). the cortical activity (EEG), (2). the hearing threshold and (3). the amplitudes and latencies of the ABR waves evoked by a stimulus of high intensity (100 dB) were investigated in guinea pigs. All animals injected (i.p.) with 100mg/kg PTZ or with 2mg/kg 4-AP developed generalized seizures, followed by characteristic EEG patterns for the post-ictal period, that were accompanied by a marked reduction of the hearing sensitivity (as indicated by the elevated threshold of the ABR), as well as by retro-cochlear changes (as judged by the changes in the later ABR waves in response to 100 dB). For instance, both convulsing agents decreased the amplitude and increased the latency of P4, that is the wave component of the ABRs generated in the lateral superior olivary nucleus and while PTZ increased the latency of P3, the wave component of the ABRs generated in the medial superior olivary nucleus, 4-AP dramatically increased its amplitude. Comparison of recordings taken at specific times for the duration of the post-ictal period (i.e. within about 1h for PTZ and 2h for 4-AP) reveals that the extent of the changes on the EEG matches with the increase in the auditory threshold and with the extent of the changes on the later waves of the ABR elicited by 100 dB. These data indicate that changes in the activity of the lateral and the medial nuclei of the superior olivary complex (SOC) accompany the hearing loss and the post-ictal epileptic cortical activity.     

No auditory conduction abnormality in children with attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioral developmental disorder characterized by lack of sustained attention and hyperactivity. It has been suggested that asymmetrical conduction of the auditory stimulus in the brainstem plays a role in the pathophysiological process of ADHD. In the present study, the functional integrity of the central auditory pathway was assessed using the auditory brainstem response (ABR), mid-latency response (MLR) and slow vertex response (SVR). Twenty ADHD children and twenty controls were recruited for the study and recordings were done on a computerized evoked potential recorder using the 10-20 system of electrode placement. There emerged no significant difference in absolute peak latencies, interpeak latencies and amplitude of ABR or latency of MLR in the ADHD children as compared with the controls. Prolongation of the SVR latency was found in the children with ADHD versus the controls, but the difference was statistically insignificant. The present study does not suggest any auditory conduction abnormality as a contributory factor in ADHD.     

Postnatal expression of the serotonin transporter in auditory brainstem neurons

To investigate the putative role of serotonin (5-HT) in auditory brainstem development, the expression of the 5-HT transporter (5-HTT) was evaluated in the normal mouse brainstem at 6 different postnatal ages. The brains of C3H/HeJ mice at birth (P0) and P1, P8-P9, P13, P21-P22, P35-P36 and P48-P50 were collected and processed immunohistochemically with an antibody raised against the 5-HTT. 5-HTT immunoreactivity (5-HTT-IR) was first observed in P8 mice and was localized to cell bodies in the ventral cochlear nucleus (VCN) and principal nuclei of the superior olivary complex, including the medial nucleus of the trapezoid body. Labeled neurons were found in similar regions in older mice except at P48-50, where labeled neurons were observed in the VCN only. 5-HTT-IR was especially prominent in VCN neurons at P21 and was observed in all of the brains examined at this age. These results indicate that auditory brainstem neurons of the normal inbred mouse express the 5-HTT postnatally. The presence of 5-HTT-IR in neurons located in the VCN indicates a regional expression of the 5-HTT that is related to the ascending auditory pathway. The timing of 5-HTT expression indicates that 5-HT may modulate developmental processes that rely on cochlear input.     

Functional and morphometrical maturation of the brainstem auditory pathway

The correlation between the functional and morphological maturation of the auditory pathway was studied in preterm and term infants, children and adults. As to the auditory brainstem response (ABR), peak latencies and I-V interpeak latencies (central transmission) gradually decreased during the third trimester and the first 2 years postnatally. The calculated pontine auditory conduction velocity (PACV) showed dramatic development, which may indicate a more precise auditory function. The PACV value at the age of 2-4 years was almost the same as that of adults. In a histomorphometrical study, the density of nerve cells in the cochlear nucleus and the inferior colliculus was found to decrease with age, that in the inferior colliculus decreasing more slowly. Myelination in the lateral lemniscus proceeded from the late fetal to the infantile period, and the myelin sheaths of large diameter increased mainly in the infantile period. Thus, on studying ABR in combination with the quantitative histomorphometrical investigation, the development of PACV was found to be related to the maturation of nerve cells in the upper nuclei corresponding to each latency as well as myelination of small and large fibers in the auditory pathway. PACV, which can be calculated by studying ABR and magnetic resonance imaging, may be used to assess more accurately the brainstem function in individual patients.     

Cortical auditory system maturational abnormalities in children with autism disorder: an MEG investigation

Latency of electric (e.g., P1 and N1) and magnetic (e.g., M100) auditory evoked components depends on age in typically developing children, with longer latencies for younger (4-6 years) and shorter, adult-like latencies for older (14-16 years) children. Age-related changes in evoked components provide indirect measures of auditory system maturation and reflect changes that occur during development. We use magnetoencephalography (MEG) to investigate maturational changes in cortical auditory systems in left (LH) and right (RH) hemispheres in children with autism disorder (AD) and Controls. We recorded auditory evoked responses over left and right temporal lobes in 17 Control and 15 AD children in the age range 8-16 years and measured M100 latency as a function of age, subject group and hemisphere. Linear regression analyses of age and M100 latency provided an estimate of the rate of latency change (ms/year) by hemisphere and subject group. Controls: M100 latency for the group ranged from 100.8 to 166.1 ms and varied linearly in both hemispheres, decreasing at a rate of -4 ms/year (LH) and -4.5 ms/year (RH). AD: M100 latency ranged from 116.2 to 186.2 ms. Slopes of regression lines did not differ from zero in either LH or RH. M100 latency showed a tendency to vary with age in LH, decreasing at a rate of -4.6 ms/year. M100 latency in RH increased slightly (at a rate of 0.8 ms/year) with age. Results provide evidence for a differential auditory system development in AD children which may reflect abnormalities in cortical maturational processes in AD.     

ABR and auditory P300 findings in children with ADHD

Auditory processing disorders (APD), also referred as central auditory processing disorders (CAPD) and attention deficit hyperactivity disorders (ADHD) have become popular diagnostic entities for school age children. It has been demonstrated a high incidence of comorbid ADHD with communication disorders and auditory processing disorder. The aim of this study was to investigate ABR and P300 auditory evoked potentials in children with ADHD, in a double-blind study. Twenty-one children, ages between 7 and 10 years, with a primary diagnosis of ADHD, participated in this experiment. Results showed that all children had normal ABR with normal latency for wave V. Results also showed that among 42 ears combined 52.38% did not have P300. For the medicated subjects we observed that among 28 ears, 42.85% did not have P300 and for the non-medicated 71.43% (N = 14 ears) did not have P300. Our results suggest that the medicated subjects had more presence of P300 (57.15%) than the non-medicated group (28.57%), though the absence of these potentials were high among the group--52.38%.     

Binaural interaction of the auditory brain-stem potentials and middle latency auditory evoked potentials in infants and adults

Binaural interactions in brain-stem auditory evoked potentials and in middle latency auditory evoked potentials were studied in 18 normal hearing adults and 10 normal term infants. Binaural interactions at the times of ABR waves V and VI were comparable in term infants and adults. Binaural interaction during the time domain of the middle latency auditory evoked potentials was the greatest at N20 in term infants and at N40 in adults. Measurement of binaural interaction during maturation may be a useful tool in assessing neurologically affected infants.     

The effects of temperature and acute alcohol intoxication on brain stem auditory evoked potentials in the cat

The effects of core temperature changes (less than 1 degree C) and acute ethanol intoxication (100-400 mg%) on brain stem auditory evoked potentials in cats were studied independently--then together--to distinguish between a putative direct pharmacological action of ethanol on brain stem auditory neurons, as reflected in reported BAEP latency changes, and in indirect action of ethanol mediated through slight changes in central temperatures. The results suggest that the reported BAEP latency effects are attributable, largely if not entirely, to the second mechanism above. No significant temperature-independent BAEP latency alterations occurred at any sublethal blood ethanol concentration or in one dosage that subsequently proved fatal. These findings do not exclude a direct ethanol effect on brain stem auditory neurons but provide no evidence for a temperature-independent effect. Knowledge of secondary BAEP temperature effects associated with drug administration is crucial to proper interpretation of BAEPs in both experimental and clinical applications.     

Circadian variation in the latency of auditory brainstem response]

The auditory brainstem response (ABR) has been found to reflect many pathological conditions within the auditory system and brainstem. And now, many neurosurgeons are using it to monitor the integrity of the auditory pathway during neurosurgical procedures. It is said that ABR shows little variation from person to person or laboratory to laboratory, nor is it easily affected by anesthesia, level of consciousness, fluctuation of blood pressure or hypoxemia. On the other hand, previous studies have shown that component waves of the ABR increase in latency and decrease in amplitude with lowered temperature. We reported here that naturally occurring circadian variations in body temperature were correlated with similar changes in the latency of the ABR. Tympanic temperature (Tty), deep forehead temperature (Thd) and ABR were recorded every 3 hours during a 24-hour period for a total of 8 recording sessions from each of 6 healthy persons (2 males and 4 females, mean age 24.3 years). The subjects were free to come and go during the day but slept overnight in the laboratory. All subjects had circadian variations in each temperature on the order of one degree. Thd had a tendency to fluctuate and its range of difference from Tty was -0.5-0.4 degree C. There was a more significant negative correlation between the latency of the ABR and Tty than that of Thd. It has become apparent that ABR latency is affected by small temperature changes such as circadian variation. The rate of a latency change in the ABR was 0.15msec per degree (C).(ABSTRACT TRUNCATED AT 250 WORDS)     

Positive auditory cortical responses in patients with absent brainstem response

ObjectiveTo compare the detectability of the different auditory evoked responses in patients with retrocochlear lesion.MethodsThe 40-Hz auditory steady state response (ASSR) and the N1m auditory cortical response were examined by magnetoencephalography in 4 patients with vestibular schwannoma, in whom the auditory brainstem response (ABR) was absent.ResultsApparent N1m responses were observed despite total absence of the ABR or absence except for small wave I in all patients, although the latency of N1m was delayed in most patients. On the other hand, clear ASSFs could be observed only in one patient. Very small 40-Hz ASSFs could be detected in 2 patients (amplitude less than 1 fT), but no apparent ASSFs were observed in one patient, in whom maximum speech intelligibility was extremely low and the latency of N1m was most prolonged.ConclusionThe N1m response and 40-Hz ASSR could be detected in patients with absent ABR, but the N1m response appeared to be more detectable than the 40-Hz ASSR.SignificanceCombined assessment with several different evoked responses may be useful to evaluate the disease conditions of patients with retrocochlear lesions.     

Temporal relationship between single unit activity in superior olivary complex and scalp-derived auditory brainstem response in guinea pig

Single unit activities in the region of the superior olivary complex were recorded from 8 guinea pigs concurrently with the recording of auditory brainstem potentials from the scalp. At any one anatomical site, be it a fiber tract (e.g. trapezoid body) or a nucleus (e.g. medial nucleus of the trapezoid body), the modal latency of the onset discharge of the units encountered corresponded in time with the latencies of several different waves (waves P2-P5) of the auditory brainstem response (ABR). Moreover, at the time of occurrence of just one of the ABR waves, single units in several diverse anatomical sites in and around the superior olive were found with modal latencies of onset discharge at that same time period. The slopes of the latency/intensity functions for both the peaks of the ABR and the modal latency of the onset discharge for most of the single units studied in the superior olive and its adjacent fiber tracts were remarkably similar. These data support the hypothesis of multiple rather than single generator site(s) for components of the ABR, at least, for waves P2-P5 in the guinea pig. These data do not distinguish whether the ABR are generated in part by travelling nerve action potentials or graded synaptic events.     

Auditory brain-stem evoked potentials in cat after kainic acid induced neuronal loss. II. Cochlear nucleus.

Auditory brain-stem potentials (ABRs) were studied in cats for up to 6 weeks after kainic acid had been injected unilaterally into the cochlear nucleus (CN) producing extensive neuronal destruction. The ABR components were labeled by the polarity at the vertex (P, for positive) and their order of appearance (the arabic numerals 1, 2, etc.). Component P1 can be further subdivided into 2 subcomponents, P1a and P1b. The assumed correspondence between the ABR components in cat and man is indicated by providing human Roman numeral designations in parentheses following the feline notation, e.g., P2 (III). To stimulation of the ear ipsilateral to the injection, the ABR changes consisted of a loss of components P2 (III) and P3 (IV), and an attenuation and prolongation of latency of components P4 (V) and P5 (VI). The sustained potential shift from which the components arose was not affected. Wave P1a (I) was also slightly but significantly attenuated compatible with changes of excitability of nerve VIII in the cochlea secondary to cochlear nucleus destruction. Unexpectedly, to stimulation of the ear contralateral to the injection side, waves P2 (III), P3 (IV), and P4 (V) were also attenuated and delayed in latency but to a lesser degree than to stimulation of the ear ipsilateral to the injection. Changes in binaural interaction of the ABR following cochlear nucleus lesions were similar to those produced in normal animals by introducing a temporal delay of the input to one ear. The results of the present set of studies using kainic acid to induce neuronal loss in auditory pathway when combined with prior lesion and recording experiments suggest that each of the components of the ABR requires the integrity of an anatomically diffuse system comprising a set of neurons, their axons, and the neurons on which they terminate. Disruption of any portion of the system will alter the amplitude and/or the latency of that component.     

Midlatency auditory evoked responses: differential effects of sleep in the human

Middle latency responses (MLRs) in the 10-100 msec latency range, evoked by click stimuli, were studied in 14 adult volunteer subjects during sleep-wakefulness to determine whether such changes in state were reflected by any MLR component. Evoked potentials were collected in 500 trial averages during continuous presentation of 1/sec clicks during initial awake recordings and thereafter during a 2 h afternoon nap or all-night sleep session. Continuously recorded EEG, EOG and EMG were scored for wakefulness, stages 2-4 of slow wave sleep (SWS), and rapid eye movement (REM) sleep during each evoked potential epoch. The major components included in this study and their latency ranges, as determined by peak latency measurements from the awake records, were: ABR V, 5-8 msec, Pa, 30-40 msec, Nb, 45-55 msec, and P1, 55-80 msec. In agreement with previous reports, ABR V and Pa showed no amplitude changes from wakefulness to either SWS or REM. Not previously reported, however, was the dramatic decrease and disappearance of P1 during SWS and its reappearance during REM to an amplitude similar to that during wakefulness. This unique linkage between a particular evoked potential component and sleep-wakefulness indicates that its generator system must be functionally related to states of arousal. Relevant data from the cat model suggest that the generator substrate for P1 may be within the ascending reticular activating system.     

Childhood developmental changes in the auditory P300

In this study we investigated developmental changes in the auditory P3 latency from childhood to adolescence. Event-related potentials evoked by improbable auditory stimuli were recorded from 35 normal children between the ages of 5 and 13 years. Regression analyses showed significant age trends in the auditory P3 latency. Latencies decreased at a rapid rate (Cz: 20.34 msec/yr; Pz: 19.27 msec/yr) from childhood to adolescence, suggesting an increased efficiency in processing information as children mature. This rate was linear or constant in nature as evidenced by the failure of the quadratic and cubic components to significantly increase predictability of the regression equation. The slope of the P3 latency/age regression line was also shown to be influenced by the interactive effects of task difficulty and maturation. It was hypothesized that neuro-developmental processes (increased myelination and dendritic arborization) may underlie the maturational changes observed in the P3 latency during childhood.     

Memory-dependent auditory evoked potentials to change in the binaural interaction of noise signals.

When non-identical binaural noise signals suddenly become coherent in the two ears, or coherent noise suddenly becomes incoherent, long latency binaurally evoked potentials (BINEP) are elicited which consist of P70, N130 and P220 components. Responses of similar morphology and latency were recorded to a change in the frequency of monaural click trains. The responses to onset or offset of the click trains were 20-50 msec shorter in latency. BINEP are also evoked when the sound image suddenly shifts due to the introduction of a short inter-aural delay in coherent noise signals. Responses to "isolated" shifts occurring once every 7 sec were 2-3 times (N130) or 3-5 times (P220) larger than responses to "frequent" shifts (6/7 sec) of the same magnitude in the same direction. Responses to "infrequent" shifts (1/7 sec) interspersed with frequent shifts in the opposite direction were of intermediate size, significantly larger than frequent responses. The BINEP could reflect the activity of location-specific neurones in the auditory cortex, but it seems more likely that they are due to a common neuronal pool responsive to any shift in the location of the sound image. Similar neuronal pools may be concerned with the detection of change in other auditory dimensions such as pitch. The difference between isolated, infrequent and frequent responses suggests that the BINEP amplitude is dependent on a memory of the shifts which have occurred in the preceding few seconds. The underlying process may be similar or identical to that which governs generation of the "mismatch negativity."     

Anesthesia effects: auditory brain-stem response

Auditory brain-stem responses (ABRs) were measured in the awake state and with ketamine and xylazine anesthesia in adult gerbils. Surface recorded vertex-positive components of the ABR were analyzed with respect to the awake and anesthetized states as a function of stimulus frequency. ABR thresholds were not altered with ketamine/xylazine. Small increases in peak latency were associated with anesthesia for all components except wave P1. Increases in absolute latency were progressively greater for successive peaks, reaching an average shift of 0.41 msec for wave P6. Amplitude changes with anesthesia were more variable, with increases generally seen for waves P4 and P6. Significant anesthesia effects on peak latency and amplitude were independent of stimulus frequency. These data confirm previously reported ABR sensitivity to non-barbiturate anesthesia. Direct comparisons of ABR interpeak intervals or amplitude ratios from awake versus anesthetized animals must account for the effects of barbiturate and non-barbiturate agents. However, the stability of response threshold and the small magnitude of latency and amplitude changes with a ketamine and xylazine regimen demonstrate that accurate electrophysiological measures of hearing sensitivity and auditory brain-stem activity can be obtained in anesthetized animals, provided that temperature and other parameters are maintained within normal physiological limits.     

The pattern of auditory brainstem response wave V maturation in cochlear-implanted children.

OBJECTIVE: Maturation of acoustically evoked brainstem responses (ABR) in hearing children is not complete at birth but rather continues over the first two years of life. In particular, it has been established that the decrease in ABR wave V latency can be modeled as the sum of two decaying exponential functions with respective time-constants of 4 and 50 weeks [Eggermont, J.J., Salamy, A., 1988a. Maturational time-course for the ABR in preterm and full term infants. Hear Res 33, 35-47; Eggermont, J.J., Salamy, A., 1988b. Development of ABR parameters in a preterm and a term born population. Ear Hear 9, 283-9]. Here, we investigated the maturation of electrically evoked auditory brainstem responses (EABR) in 55 deaf children who recovered hearing after cochlear implantation, and proposed a predictive model of EABR maturation depending on the onset of deafness. The pattern of EABR maturation over the first 2 years of cochlear implant use was compared with the normal pattern of ABR maturation in hearing children. METHODS: Changes in EABR wave V latency over the 2 years following cochlear implant connection were analyzed in two groups of children. The first group (n=41) consisted of children with early-onset of deafness (mostly congenital), and the second (n=14) of children who had become profoundly deaf after 1 year of age. The modeling of changes in EABR wave V latency with time was based on the mean values from each of the two groups, allowing comparison of the rates of EABR maturation between groups. Differences between EABRs elicited at the basal and apical ends of the implant electrode array were also tested. RESULTS: There was no influence of age at implantation on the rate of wave V latency change. The main factor for EABR changes was the time in sound. Indeed, significant maturation was observed over the first 2 years of implant use only in the group with early-onset deafness. In this group maturation of wave V progressed as in the ABR model of [Eggermont, J.J., Salamy, A., 1988a. Maturational time-course for the ABR in preterm and full term infants. Hear Res 33, 35-47; Eggermont, J.J., Salamy, A., 1988b. Development of ABR parameters in a preterm and a term born population. Ear Hear 9, 283-9] of normal hearing children: a sum of two decaying exponential functions, one showing an early rapid decrease in latency and the other a slower decrease. Remarkably, the time-constants fell well within the ranges described by Eggermont and Salamy (i.e., 3.9 and 68 weeks), consistent with the time-course of the neurophysiological mechanisms presumably involved in auditory pathway maturation during the first 2 years of life: i.e., myelination and increased synaptic efficacy. In contrast, relatively little change in wave V was evident in children with late-onset deafness. In agreement with the notion that EABR maturation follows an apex-to-base gradient as described for ABR, we observed that wave V latencies were longer for the basal than the apical end of the implant electrode array and remained so throughout the study period, whatever the time of onset of deafness. CONCLUSIONS: The findings in the early-onset of deafness group support the theory that auditory pathways remain "frozen" during the period of sensory deprivation until cochlear implant rehabilitation restores the normal chronology of maturational processes. In children with late-onset deafness, however, some maturational processes may occur before the onset of deafness, and thus less additional maturation is required during the first two years of implant use resulting in no significant EABR latency changes being observed in this period. The results suggest that the rehabilitation-induced plasticity of the auditory pathways is, in case of late auditory deprivation, unlikely to result in neurophysiological outcomes similar to those observed in children with early auditory deprivation. SIGNIFICANCE: Changes in EABR wave V latency over the first 2 years of cochlear implant use were found to be well fitted by the sum of two decaying exponential functions in children with early-onset deafness. This is in line with the maturation of ABR wave V latency in normal-hearing children over the first two years of life. Further studies are needed to assess whether the differences observed in terms of auditory pathways maturation are associated with consistent differences in terms of language development.     

面肌痉挛显微血管减压术中脑干听觉诱发电位监测的应用

目的 研究脑干听觉诱发电位(BAEP)监测在显微血管减压术(MVD)治疗面肌痉挛手术中的应用.方法 回顾性分析90例面肌痉挛患者在MVD术中进行BAEP监测的临床资料.结果 MVD手术操作过程均可引起BAEP改变,包括:BAEP的Ⅰ、Ⅲ、Ⅴ波绝对潜伏期明显延长(P＜0.01),Ⅰ～Ⅲ、Ⅲ～Ⅴ、Ⅰ～Ⅴ波间期明显延长(P＜0.01),Ⅲ波、Ⅴ波波幅明显降低(P＜0.01);有16例术中Ⅴ波绝对潜伏期延长超过1ms,Ⅰ波波幅也有明显降低(P＜0.01),但术后无听力障碍;手术结束时Ⅲ～Ⅴ波间期及16例的Ⅰ、Ⅴ波波幅恢复较快.2例术后患侧听力丧失的患者中,1例术中Ⅴ波波幅逐渐降低至消失,另1例术中未监测到Ⅴ波波形.结论 MVD手术操作过程均可引起BAEP改变;Ⅴ波绝对潜伏期延迟超过1ms者相对多见,但无听力受损;Ⅴ波波幅下降程度可为术中神经功能受损提供客观指标,以采取相应措施减少听力并发症的发生.