Source derivation of the brain-stem auditory evoked potential

This study described the results of applying source derivation to the brain-stem auditory evoked potential. Unilateral stimulation gives rise to current sinks, associated with waves I and III, which are located in the vicinity of the ipsilateral mastoid. Waves II and V are associated with a pair of current sinks which appear bilaterally in the vicinity of each mastoid.     

Maturation of the brain-stem auditory evoked potential in premature infants

Patterns of development and extent of variability of the brain-stem auditory evoked potential (BAEP) are described in 52 healthy premature infants and 50 normal term newborns with reliable conceptional ages. Binaural and monaural stimulation are compared. Serial studies of individual prematures are emphasized and demonstrate that the most consistent and least variable measures are the monaurally derived interpeak intervals. All the BAEP parameters studied mature including wave form, relative amplitude, peak and interpeak intervals, but there is far more variability in preterms than in term infants or adults, even when infants are carefully matched for conceptional age. As term is approached, BAEP variability decreases substantially, suggesting that near term the BAEP becomes a more reliable indicator of neurologic function. The variability of the BAEP in the normal preterm limits its usefulness in determining neurologic dysfunction in individual high risk infants. Nevertheless, the BAEP may still prove useful for defining group differences among infants and could provide an objective measure of those factors influencing neurologic development. Serial change in the BAEP is a specific parameter which we believe merits further study in premature infants as an index of neurologic maturation.     

Effects of hypothermia on the cat brain-stem auditory evoked response

Effects of systematic hypothermia on the brain-stem auditory evoked resposes (BAERs) in 4 pentobarbital anesthetized adult cats placed on total cardiopulmonary bypass were investigated. Hypothermia was achieved by slowly cooling the bypass blood through a heat exchanger. Serial BAERs were recorded at 2 min intervals as brain temperature was lowered from 37 to 22°C and then rewarmed over a 1–2 h period. Temperatures were recorded from the brain, esophagus and rectum. Three effects were produced by controlled systemic hypothermia. First, latencies of each component wave (I–V) of the BAER increased exponentially as brain temperature was lowered to 19°C. Latencies of earlier waves (I–III) increased less than those of the later waves (IV–V). Arrhenius plots of inverse latency (rate) versus reciprocal of the absolute temperature generated a family of straight lines of similar slope for each of the 5 component waves of the BAER. The activation energy for each of the 5 BAER waves was derived from the slope of the Arrhenius plot. The mean and standard deviation of the activation energy of all 5 waves was 9.7 ± 0.5 kcal/mole°C. The fact that the activation energy was similar for each BAER component wave (I–V) indicated that the increase in latencies for all 5 waves was governed by the same rate-limiting, temperature-dependent process(es). Second, the rise time and duration of each of the component waves of the BAER increased with decreasing temperature, Third, wave amplitudes increased from 37 to 32°C in a quasiparabolic relation and then, decreased at approximately a linear rate. The BAER wave form completely disappeared below 20.3°C. Slow rewarming of the brain to its initial temperature restored the BAER component waves to their original latencies and amplitudes.     

Effects of ketamine anesthesia on the rat brain-stem auditory evoked potential as a function of dose and stimulus intensity

Because ketamine is both an abused substance and a commonly used veterinary anesthetic, its effects on brain and sensory functions are of interest. The present study examined the dose-dependent effects of ketamine anesthesia in the rat, using the brain-stem auditory evoked potential (BAEP) as an objective, quantitative measure of this substance's acute effects on brain and sensory electrophysiology. The animal subjects were 11 young adult female Long-Evans rats. BAEPs were recorded from skull screw electrodes during a baseline period as well as after saline and ketamine treatments. Ketamine was administered (i.p.) in 2 serial doses. The first dose (100 mg/kg) was followed 30-40 min later by a second dose (also 100 mg/kg). Equal volumes of normal saline were also injected serially. An interval of 1-2 weeks occurred between the saline and ketamine treatments, with treatment order counterbalanced. Normothermia was maintained to control for possible temperature-related effects. Ketamine produced prolongations in the latencies of all BAEP components (P1 through P6) that were statistically significant relative to baseline values. These latency shifts were progressively greater for waves P1 through P4 (shifts in P5 and P6 approximated the P4 shift). The effect of the second ketamine injection was to nearly double the latency shifts. Ketamine also had significant and complex effects on BAEP amplitudes that were dependent on dose and stimulus intensity. The results of the present study challenge the belief that the BAEP is resistant to the effects of anesthetics and suggest that the BAEP is useful in characterizing the CNS and sensory effects of these pharmacological agents.     

Does selective attention influence the brain-stem auditory evoked potential?

We have re-examined the problem of selective attention in relation to brain-stem auditory evoked potentials (BAEPs). We compared BAEPs recorded in the relaxed individual with those elicited during visual attention and during auditory attention. Particular emphasis was placed on the use of a demanding visual task to ensure appropriately sustained levels of concentration by the subject for the durations of the tests. We measured the latency of wave I, the wave I-V interval and the amplitudes of waves I and V in 16 subjects in each of the conditions but could find no effect attributable to changes in states of attention. We conclude that there is no evidence for the actions of gating or switching mechanisms at early stages of the auditory pathways.     

Analysis of brain-stem auditory evoked potential and visual evoked potential in patients with Parkinson disease

INTRODUCTION The exact cause of Parkinson disease (PD) has not been known yet[1]. The overwhelming progress had been made in the treatment and pathogenesis of PD in recent 30 years, especially 10 years[2]. But it is still no way now to prevent or postpone…     

Emergence of the brain-stem auditory evoked potential in the premature lamb.

Brain-stem auditory evoked potentials (BAEPs) were elicited by bone conducted stimuli in the very immature lamb following delivery, wherein liquid ventilation techniques were utilized to control cardiopulmonary and acid-base conditions, independent of umbilical-placenta support. Unlike previous studies of the in utero fetal lamb in which the BAEP could not be elicited by earphone delivered stimuli until 117 days gestation, our results demonstrate that the BAEP emerges at least as early as 106 days gestation in the lamb and consists of a full complement of readily discernible and reproducible wave forms. In addition, the results demonstrate substantial maturation of the BAEP from 106 to 122 days gestation during which time there is a significant decrease in absolute and interpeak latencies with an increase in developmental age. It is concluded that the ability to elicit the BAEP utilizing bone conduction at this early stage of gestation is related to improved stimuli delivery. Furthermore, this study demonstrates the feasibility and flexibility afforded by liquid ventilation and bone conduction BAEP techniques to study brain-stem function at particularly vulnerable stages of development.     

Neuroanatomic correlations with the late waves of the brain-stem auditory evoked potential

The goal of this study was to investigate the neuroanatomic correlations of the late waves (VI-VIII) of the BAEP. Patients (N = 55) with clinical evidence of a CVA were compared to a normal control group (N = 85). Latencies of greater than 3 S.D. from the means of the normal group were considered abnormal. CT and MRI scans provided evidence of the lesions. For the 14 patients who had normal BAEPs, the sizes of lesions were significantly smaller than for those with abnormal tests. Evidence shows that an abnormal wave VI was related to an ipsilateral cortical lesion and an abnormal wave VIII was related to a lesion in the internal capsule-corpus striatum.     

Effects of cholinergic blockers on auditory brain-stem evoked potentials in rats.

The pharmacology of auditory brain-stem evoked potentials (ABEP) pathways is poorly understood. There are anecdotal reports on the involvement of various neurotransmitters but they were not investigated systematically. The aim of this study was to investigate the effects on ABEP of muscarinic and nicotinic blockers, administered into the cerebral ventricles. Atropine sulfate, d-Tubocurarine and saline were injected stereotactically into the lateral cerebral ventricle of anesthetized male rats. Auditory clicks were given at a rate of 20 s(-1). ABEP recording was performed before and 30 min after injection. Pre- and post-injection peak latencies and peak-to-peak amplitudes of positive waves were compared for each animal. Atropine reduced the amplitudes of waves P1, P3 and P4 and increased mildly the brain stem transmission time. d-Tubocurarine reduced the amplitudes of P1 and P4 with no significant effect on the peak latencies. Saline injection had no effect on any of the parameters. These results show that both cholinergic systems are involved in ABEP generation or transmission. Mechanism of action could be either direct inhibition of afferent pathways or indirect effect, via modulating efferent pathways.     

Age-related latency changes in the brain-stem auditory evoked potentials

The effects of age on the brain-stem auditory evoked potentials were studied on 156 healthy subjects with ages ranging from 18 to 76 years. The latencies of peaks I-VII and the interpeak latencies of I-III, III-V and I-V were consistently shorter for the female group than the male group. The females also had higher peak amplitude than the males. The effects of sex on the peak and interpeak latencies were observed in all age groups. There was a small progressive prolongation in the peak latency with increasing age, particularly peak V. Although a correlation between the age and the I-III interval was not observed, there was also a small increase with age in the interpeak latencies of III-V and I-V.     

The effects of experimental brain-stem ischaemia on brain-stem auditory evoked potentials in primates.

We related intracranial auditory brain-stem evoked potentials (BAEPs) to the surface BAEP using a model of focal brain-stem ischaemia. In 17 baboons anaesthetised with alpha-chloralose, BAEPs were recorded bilaterally at the mastoids and in the caudal lateral lemniscus (LL) and inferior colliculus (IC), in response to monaural click stimulation. Electrodes at these sites were each connected to the positive input of a differential amplifier, and one other electrode, placed at the vertex, was connected to all the negative inputs. Measurements of local cerebral blood flow (CBF) by hydrogen clearance were made at the LL and IC sites. The LL wave form contained 5-7 positive peaks, the second (B wave) being dominant and coinciding with the negative wave II of the surface BAEP. Following graded ischaemia, produced by basilar artery occlusion and controlled hypotension, the latency changes of these two peaks were significantly correlated, as were those of the third wave (C wave) of the LL response and the surface wave III. In the IC, the contralateral wave form contained 4 positive waves (A-D) and a later, dominant, slow negative wave; changes in its peak latency and those of the slow negative surface wave were similarly correlated. The thresholds of local CBF for increases in latency of waves B and C in the LL were similar (12-15 ml/100 g/min), but in the IC the thresholds were 20, 30-35 and 20-24 ml/100 g/min for the B, C and slow negative waves, respectively. Our data indicate that a gradient of sensitivity to ischaemia is present along the brain-stem auditory pathways; this could explain the earlier change of the late, rather than early, BAEP components as reported in clinical cases involving brain-stem lesions.     

Correlation between a unilateral midbrain-pontine lesion and abnormalities of brain-stem auditory evoked potential

Brain-stem auditory evoked potentials (BAEPs) were evaluated over a 39 day period in a patient with a unilateral pontine-midbrain lesion verified by CAT scan and at autopsy. Waves I, II and III were present on the side of lesion, whereas all 5 waves were present on the side opposite the lesion. The findings suggest that the BAEPs may be obtained with only an intact ipsilateral auditory pathway. Crossing fibers in the trapezoid body also appear to make contributions to the normal generation of wave V.     

Latency compensation analysis of the auditory brain-stem evoked response

Latency compensation analysis (LCA) was applied to single trial samples of the auditory brain-stem evoked response (ABR, IV-V complex). By this means it was possible to characterize properties of temporal variability in the ABR, including certain cases of temporal outliners. A lagged cross-correlogram analysis provided information for each trial that included the largest r2 and associated lead/lag value. The distribution of lag values (based on all trials) was statistically different when ABRs were evoked by stimuli differing by 5 dB. Recomputing the ABR by eliminating temporal outliers, and by adjusting for temporal variability, showed a range of individual patterns of increased amplitude. However, a comparison of Down syndrome (DS) and non-retarded individuals showed a significantly greater amplitude increase in the DS group after LCA. This suggests that certain forms of mental retardation may be characterized by reduced stability in a neural system that is thought to depend upon 'synaptically secure' neurons.     

Age-dependent amplitude variation of brain-stem auditory evoked potentials

Normative amplitude values of brain-stem auditory evoked potential (BAEP) components are given for normally hearing subjects at 1, 10, 30, 50 and 70 years of age, with an intragroup age variation of only +/- 6 months. Under these circumstances amplitude standard deviations decreased to less than 20% of the mean values. In contrast with the reduced evolution of latency with age, BAEP amplitude (for components I-V) undergoes a greater oscillation during ontogeny. With the exception of component I, it increased markedly from 1 year to 10 years of age and decreased thereafter constantly up to 50 years, with a mean rate of 10 nV yearly. The decrease slowed down between 50 and 70 years. The amplitude differences between the subgroups are highly significant statistically (P less than 0.01). Possible reasons for these changes are discussed.     

Brain-stem auditory evoked potential abnormalities with unilateral brain-stem lesions demonstrated by magnetic resonance imaging

We correlated the brain-stem auditory evoked potential (BAEP) abnormalities in 24 patients with discrete unilateral brain-stem lesions demonstrated by magnetic resonance imaging. In 18 patients who had BAEP abnormalities either confined to or more severe on stimulation of one ear, the lesion on magnetic resonance imaging was in the brain stem ipsilateral to the corresponding ear. Mesencephalic lesions produced amplitude abnormalities of the IV/V complex while pontine lesions resulted in abnormalities of earlier components (wave II and/or III). Prolongation of the I-III interpeak latency tended to occur with pontine lesions and of the III-V interpeak latency with mesencephalic lesions. Unilateral brain-stem lesions, particularly at the mesencephalic level, often produced BAEP abnormalities on both ipsilateral and contralateral monaural stimulation.     

脑干听觉诱发电位对面肌痉挛微血管减压术中听力保护的应用

目的探讨面肌痉挛微血管减压（microvascular decompression,MVD）术中应用脑干听觉诱发电位（brain—stem auditory evoked potential,BAEP）监测,对减少术后听力损伤的应用价值。方法回顾性分析43例面肌痉挛患者术中BAEP波V波形的变化以及手术前后平均纯音听力阈值（pure tone average,PTA）的改变,经统计学分析得出术中V波潜伏期延长的警示阈值。结果MVD术中,在显露面神经和责任血管减压操作时,V波潜伏期延长最为显著。38例患者术后PTA增高小于20dB,V波潜伏期平均延长（0．60±0．43）ms。其余5例术后PTA增高大于20dB,V波潜伏期平均延长（1．07±0．35）聪。两组患者V波潜伏期延长时间存在差异（P〈0．05）。术中V波潜伏期延长大于0．6ms与患者术后听力损伤相关;术中V波潜伏期延长大于1．0ms与患者术后听力损伤密切相关。因此术中V波潜伏期延长警示闾值可设定为0．6ms和1．0ms。结论BAEP监护警示阈值有助于指导面肌痉挛MVD术操作,避免术中过度牵拉听神经,减少对其周围微循环的干扰,为术中保护听神经提供警示作用。     

Comparison of cat and human brain-stem auditory evoked potentials

Brain-stem auditory evoked potentials (BAEPs) elicited by clicks were recorded from both humans and cats. The responses of the two species were compared as functions of click level, click rate, ear stimulated, and electrode position. Since the BAEPs appear to have both high- and low-frequency components, the responses were filtered to analyze these components separately. The similarities and differences in the behavior of the peaks of the two species support the view that the first three (positive and negative) high-frequency peaks which are comparably numbered have similar generators, but the later comparably numbered peaks do not. The presence of binaural interaction beginning with P4 and PV suggests a correspondence between peaks P4 through P5 in cat with PV through PVI, respectively, in human. The similarity in behavior of these peaks also support this correspondence. Furthermore, when conduction times are estimated from interpeak latencies, this correspondence of peaks agrees more closely with the relative pathway lengths in the two species, than does the correspondence based on comparable numbering.     

Diagnostic role of brain-stem auditory evoked potentials in neurobrucellosis.

Evoked potential audiometry and brain-stem auditory evoked potentials were evaluated in 15 patients with systemic brucellosis in whom brucella meningitis was suspected clinically. In 8 patients cerebrospinal fluid (CSF) was abnormal with high brucella titre, and evoked potentials were abnormal in all of them. In 7 patients the CSF was normal and evoked potentials were also normal. Brain-stem auditory evoked potential abnormalities were categorised into 4 types: (1) abnormal wave I, (2) abnormal wave V, both irreversible, (3) prolonged I-III interpeak latencies, and (4) prolonged I-V interpeak latencies, both reversible. These findings are of important diagnostic value and correlate well with the clinical features, aetiopathogenesis and final outcome.     

Classification of brain-stem auditory evoked potentials by syntactic methods

A syntactic pattern recognition procedure for classification of brain-stem auditory evoked potential (BSAEP) is presented. A pre-processing stage of zero-phase bandpass filtering enhances the peaks and suppresses the noise. A finite-state grammar was designed to identify the peaks. Attributes of the peaks (latencies and amplitudes) that are identified are checked for their acceptability. A training run on 70 subjects of known diagnosis was performed to fine-tune the system and build up necessary acceptance criteria. Peak latency differences are used for the classification rather than absolute peak latencies. Acceptance criteria for peak latency differences were empirically optimized. A data base of normal BSAEPs, created during the training run, was updated and used during the test run. Test of the classifier using 60 subjects yielded a classification accuracy of 83%. The classifier has acceptable accuracy and can be modified for other evoked potentials such as visual and somatosensory by establishing relevant attribute tables.