Brainstem auditory evoked potentials and middle latency auditory evoked potentials in young children

Measurements of brainstem auditory evoked potentials (BAEP) and middle latency auditory evoked potentials (MLAEP) are readily available neurophysiologic assessments. The generators for BAEP are believed to involve the structures of cochlear nerve, cochlear nucleus, superior olive complex, dorsal and rostral pons, and lateral lemniscus. The generators for MLAEP are assumed to be located in the subcortical area and auditory cortex. BAEP are commonly used in evaluating children with autistic and hearing disorders. However, measurement of MLAEP is rarely performed in young children. To explore the feasibility of this procedure in young children, we retrospectively reviewed our neurophysiology databank and charts for a 3-year period to identify subjects who had both BAEP and MLAEP performed. Subjects with known or identifiable central nervous system abnormalities from the history, neurologic examination and neuroimaging studies were excluded. This cohort of 93 children up to 3 years of age was divided into 10 groups based on the age at testing (upper limits of: 1 week; 1, 2, 4, 6, 8, 10 and 12 months; 2 years; and 3 years of age). Evolution of peak latency, interpeak latency and amplitude of waveforms in BAEP and MLAEP were demonstrated. We concluded that measurement of BAEP and MLAEP is feasible in children, as early as the first few months of life. The combination of both MLAEP and BAEP may increase the diagnostic sensitivity of neurophysiologic assessment of the integrity or functional status of both the peripheral (acoustic nerve) and the central (brainstem, subcortical and cortical) auditory conduction systems in young children with developmental speech and language disorders.     

Evaluation of auditory evoked potentials from the inferior colliculus in rat

This study aimed to investigate the usefulness of auditory evoked potentials (AEPs) in rats. To this end, N1, P2 latencies, and the N1-P2 amplitude of responses to different acoustic stimuli from rats, which were implanted with permanent electrodes in the inferior colliculus (IC), were evaluated and used to demonstrate the frequency characteristics of IC region. Permanent electrodes were implanted in IC regions of 7 male albino rats by the stereotaxic method. The animals were exposed to five tones series of stimuli (1000 Hz, 2000 Hz, 4000 Hz, 6000 Hz, and 8000 Hz tones with 1500 ms interstimulus intervals) of 70 dB with a duration of 1000 ms. AEPs) were recorded and analyzed with the Brain-Data Acquisition system. There were no statistically significant differences in N1, P2 latencies, and the N1-P2 amplitude of AEPs from IC regions of rats as a result of changes in the frequency of stimulus. It was determined that the dominant frequency activity of the IC to acoustic stimulus was theta-alpha band, with theta as the peak frequency.     

Binaural vs. monaural auditory evoked potentials in rat neocortex

High spatial resolution epicortical recording techniques and numerical modeling were used to investigate laterality effects on the middle latency auditory evoked potential (MAEP) complex. Our data confirm previous reports that auditory stimulus laterality has a consistent effect on the amplitude, timing, and spatial distribution of the MAEP complex. The earliest temporal components (P1a, P1b and N1) show the greatest sensitivity, and are absent during ipsilateral stimulation. The later positive slow wave (P2) is present at the same amplitude during all stimulation conditions. Generation of the P2 appears to be independent of prior activation of areas 36 and 41 reflected in the early components, suggesting its generation by a more diffuse thalamocortical pathway, possibly from the medial division of the medial geniculate. Serial vs. parallel activation of rodent auditory cortex is discussed in the context of laterality-sensitive MAEP components.     

Brainstem auditory evoked potentials in meningomyelocele

The brainstem auditory evoked potentials (BAEP) of twenty-seven Myelomeningocele (MMC) patients were analyzed and compared with the results of a normal population. The longest wave V or V-I interpeak latencies were seen in patients with shunted hydrocephalus and cranial nerve defects. The shortest wave V and V-I interpeak latencies were found in patients without hydrocephalus. However, these latencies of MMC patients were significantly longer than the latencies of a normal population. Wave I latencies of all MMC subgroups were not significantly different from the results of the normal probands. It is assumed that V-I interpeak latency prolongation in MMC patients, which is related to the severity of the clinical signs of the Arnold Chiari malformation, is mostly due to an elongation of the brainstem.     

Polysensory evoked potentials in rat parietotemporal cortex: combined auditory and somatosensory responses

A 64 channel microelectrode array was used to map auditory evoked potentials (AEP), somatosensory evoked potentials (SEP) as well as combined auditory and somatosensory evoked potentials (ASEP) from a 7 × mm² area in rat parietotemporal neocortex. Cytochrome oxidase (CO) stained sections of layer IV were obtained in the same animals to provide anatomical information underlying epicortical field potentials. Epicortical responses evoked by click or vibrissa stimuli replicated earlier findings from our laboratory, and appeared as a family of waveforms centered on primary auditory (AI) or somatosensory (SI) cortical areas as determined from CO histology. Selective microinjections of HRP to AI and SI further confirmed their specific sensory relay nuclei in the thalamus. A small polysensory area between AI and SI, responded uniquely with an enhanced negative sharp wave to combined auditory and somatosensory stimuli. HRP retrograde labeling revealed that the thalamocortical projections to this area were from the posterior nuclear group (Po) and medial division of the medial geniculate (MGm). These data establish close relationships between epicortical AEP, SEP, and especially ASEP and corresponding cortical structures and thalamocortical projections. The neurogenesis of unimodal and polysensory evoked potentials is discussed in terms of specific and non-specific systems.     

Brainstem auditory evoked potentials in Wilson's disease

Twelve patients with Wilson's disease, aged 11-25 years, underwent brainstem auditory evoked potential (BAEP) study. The results were correlated to clinical, neuroradiological and laboratory data. Ten had prominent to severe neurological manifestations, suggestive of involvement of one or several CNS structures, and 2 were neurologically free. All had evidence of abnormal copper metabolism, and 8 had CT scan evidence of brain atrophy, or hypodense areas in basal ganglia, or both. The 2 patients without neurological manifestations as well as one with neurological signs had normal BAEP. One patient with neurological signs had increased N1 latency due to cochlear hearing loss, but normal interpeak intervals, while 8 of 10 patients with prominent neurological symptoms and signs had abnormal BAEPs (prolongation of NIII-NV interpeak interval). The value of NIII-NV interpeak interval correlated with the number of different neurological signs (neurological score) attributable to involvement of different CNS structures (r = 0.64 at P = 0.001). Abnormal BAEPs do not seem to be an early finding in Wilson's disease.     

Cue-induced auditory evoked potentials in alcoholism.

OBJECTIVE: Conditioning processes may convert neutral stimuli to drug-associated stimuli and create an implicit drug memory. Previous studies showed specific psychophysiological reactions to alcohol-associated stimuli differentiating alcohol-dependent subjects from healthy controls. This was shown in evoked potentials using visual and olfactory alcohol-related stimuli. METHODS: Our study examined the effects of complex alcohol-associated sounds in comparison to complex neutral sounds on electrophysiological event-related potentials and the self-report of craving. We assessed 10 detoxified alcoholics and 10 healthy controls in a cue-reactivity paradigm. RESULTS: Detoxified alcoholics demonstrated significantly higher alcohol stimulus-induced late P300 and late positive complexes. Subjective baseline craving and stimulus-induced craving only differed significantly between groups in terms of the craving dimension "relief of withdrawal symptoms". CONCLUSIONS: The results show that auditory stimuli attach importance to stimulus-induced craving in alcoholics. Therapeutic consequences will be discussed. SIGNIFICANCE: The study examined for the first time the effects of alcohol-associated auditory stimuli on alcohol craving and identifies learning processes as underlying neural mechanisms which support the assumption of an implicit addiction memory in alcoholics.     

Brainstem auditory evoked potentials in tuberous sclerosis

Brainstem auditory evoked potentials were recorded in 4 subjects and pattern reversal evoked potentials in 1 subject, all with tuberous sclerosis. Alterations were found (absence or delay of components and prolonged interpeak intervals) which may suggest impaired nervous conduction also at brainstem level in patients with tuberous sclerosis.

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Sommario Sono stati registrati i potenziali evocati auditivi troncoencefalici in 4 soggetti con sclerosi tuberosa, in uno di essi sono stati registrati anche i potenziali evocati visivi da pattern reversal. Sono state ritrovate alterazioni delle risposte (assenza o ritardo di alcune componenti ed intervalli interpicco prolungati) che possono suggerire l'esistenza di una conduzione nervosa alterata anche a livello del tronco dell'encefalo nei pazienti con sclerosi tuberosa.

     

Brainstem auditory evoked potentials in postconcussion syndrome

Brainstem auditory evoked potentials (BAEPs) were recorded from 55 patients with postconcussion syndrome (PCS) to elicit evidence of an organic and subclinical brainstem disorder. Fifteen patients (27.3%) showed abnormal responses unilaterally or bilaterally, especially for one or more interpeak latencies prolonged beyond the upper 99% confidence limits. Other 9 patients had borderline responses. The BAEP alterations were not correlated either with dizziness at the time of recording, or with vestibular troubles in the routine caloric test. Though BAEP abnormalities may be present a long time after injury, we found an improvement of responses in the majority of 14 re-tested patients. These data show that BAEP can give an objective demonstration of a reversible brainstem disorder in patients with PCS.

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Sommario I potenziali evocati acustici del tronco cerebrale (BAEP) sono stati registrati in 55 pazienti affetti da sindrome soggettiva postcraniotraumatica (PCS), per evidenziare un possibile danno organico subclinico del tronco cerebrale. Quindici pazienti (27.3%) hanno mostrato risposte alterate unilateralmente o bilateralmente, soprattutto a causa della presenza di una o più latenze interpicchi oltre i limiti fiduciali superiori del 99%. Altri 9 pazienti hanno mostrato risposte borderline. Non sono state ritrovate correlazioni tra il reperto di BAEP alterati e la presenza di vertigini all'atto dell'esame, né con il comportamento dell'esame vestibolare. Benché le alterazioni del BAEP si possano osservare anche a distanza di molti mesi dal trauma, la maggioranza dei pazienti con BA EP alterati, ad un secondo esame ha mostrato un miglioramento della risposta. Tali dati dimostrano che i BAEP sono in grado, in alcuni pazienti affetti da PCS, di evidenziare un danno organico del tronco cerebrale, passibile di regressione.

     

Expressed emotion and auditory evoked potentials

The expressed emotion (EE) of key relatives has been shown to predict the course of illness in psychiatric patients. In this study, we examined whether there might be physiological correlates to the EE index in nonbiological key relatives of patients with affective psychoses. High-EE and low-EE relatives were compared concerning their slopes of the amplitude/stimulus intensity function (auditory evoked N1/P2-component). We found that the slopes were clearly steeper in the case of low-EE relatives. In comparing the slopes of all key relatives with those of an age-matched control group without psychiatrically ill partners, we could find no differences. Therefore, the slope differences between high-EE and low-EE relatives do not seem to reflect differences in the illness of partners. We speculated whether a steep slope as well as low EE could be associated with an action-oriented, impulsive communication style, which would prevent the development of an affectively tense communication pattern.     

Brainstem auditory evoked potentials in Chiari-II malformation

Brainstem function in patients with Chiari-II malformation was evaluated by brainstem auditory-evoked potentials (BAEPs). All cases had associated hydrocephalus, some of which were shunted. The effect of the shunting operation on the wave forms was examined as well as the age-wave relationships. Although the shunting operation resulted in shortened brainstem conduction time, the overall postshunt responses were still far from normal. Another significant finding was that whereas there were remarkable abnormalities in recorded wave-forms in cases younger than 8 years, normal or almost normal responses were obtained in all cases older than 8. BAEP abnormalities could not be correlated with the severity of meningomyelocele, nor was the predictive value of response in assessing potential risk of symptomatic Chiari malformation established.This paper was presented at the 15th Annual Meeting of the International Society for Pediatric Neurosurgery, New York, July 12–16, 1987     

Surgical monitoring with auditory evoked potentials

This comprehensive review of surgical monitoring with auditory evoked potentials (AEPs) includes a detailed discussion of techniques used for recording brainstem auditory evoked potentials, direct eight-nerve potentials, and electrocochleograms. The normal waveform of these different potentials is discussed, and the typical patterns of abnormalities seen with different insults to the peripheral or central auditory pathways are presented. The mechanisms most probably responsible for changes in AEPs during surgical procedures are analyzed. A critical analysis is made of what represents a significant change in AEPs. Also considered is the predictive value of intrasurgical changes of AEPs. Finally, attempts are made to determine whether AEPs monitoring can assist the surgeon in the prevention of postsurgical complications.     

Sensation seeking and auditory evoked potentials

The relationship between auditory evoked potentials (AEP) and the German version of Zuckerman's Sensation Seeking Scale was examined. The slope of the amplitude/stimulus intensity function (N1/P2 component) and the N1 latency were particularly studied, as these variables have been found to be potential predictors of the response to lithium prophylaxis. Thirty-three healthy subjects participated in two testing series on the first day and in a third run 3 weeks later. Binaural clicks at four intensity levels (58, 68, 78, 88 dB HL, ISI 2.1 sec) were presented in randomized order by headphone. Eighty responses were averaged at each intensity level. The pattern of correlation between the German version of the Sensation Seeking Scale and a personality inventory (FPI) supports the validity of the Sensation Seeking Scale. Only a tendency toward steeper slopes of the amplitude/stimulus intensity function (ASF) in high sensation seekers was observed in the first run. However, there was a significant interaction of sensation seeking and the test run. Only high sensation seekers showed an influence of retesting on the slope of the ASF, leading to a decrease of the slope in the second, compared with the first run. This might correspond to the psychological pattern of sensation seeking, which is characterized by a permanent need for new and exciting situations and, at the same time, by a rapid loss of interest in these situations. With regard to the N1 latency, a significant interaction of sensation seeking and lead was found. Low sensation seekers showed longer N1 latencies over the right than over the left hemisphere, a finding that accords with some psychophysiological theories on the relation between asymmetric hemispherical activation and certain psychological constructs. Our results support the view that sensation seeking is a personality feature that is closely related to certain physiological variables.     

Frontal auditory evoked potentials and augmenting-reducing

Auditory evoked potentials (AEPs) to tones (750 Hz--200 msec) ranging from 50 to 80 dB SPL were studied at Cz and Fz leads in 29 normal adults (15 males) ranging in age from 20 to 22. Peak-to-trough amplitudes were measured for the P1-N1 and the N1-P2 wave forms as well as baseline (500 msec prestimulus)-to-peak amplitudes for each component, i.e., P1, N1 and P2. Amplitudes were examined as a function of intensity and electrode location. Cz-Fz amplitude differences increased with increasing stimulus intensity, the differentiating peak being the N1 component. An overall reducing phenomenon was found at Fz in the 70-80 dB range whereas an augmenting effect was observed at Cz for these intensities. The augmenting/reducing groups defined by analysis of individual amplitude-intensity patterns were different whether we considered Fz or Cz results: Fz reducers were more numerous than Cz reducers. These results on prominent reducing at the frontal level were examined in relation to the data concerning the modulatory function of the frontal cortex on auditory EPs. Implications were drawn for the role of the frontal cortex in cortical augmenting-reducing.     

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.     

Human auditory evoked potentials: Reliability of intensity functions

This investigation assessed the relative reliability of the human auditory evoked potential (AEP) amplitude-intensity and latency-intensity functions. Averaged AEP waveforms to 10 levels of stimulus magnitude were obtained from bipolar recordings. Variability and slope of group functions were constant, as indicated by nonsignificant differences in day-to-day residual variances and intersession regression coefficients. Periodic change in amplitude or latency thus indicated a shift of the entire function. Individual N1–P2 amplitude-intensity functions Were similarly reliable, while individual P2–N2 amplitude and latency measures tended to be more variable. No significant differences were obtained across sessions for regression coefficients based on either group or individual data. Intersession AEP amplitude and latency apparently varied systematically with stimulus intensity.     

Brain-stem auditory evoked potentials in the rat: effects of gender, stimulus characteristics and ethanol sedation

Rat BAEPs varied significantly as a function of gender and ethanol sedation as well as stimulus intensity and repetition rate. All BAEP wave latencies decreased and amplitudes increased with increasing stimulus intensity. Contrary to the prevailing view, the I-IV interpeak latency changed significantly as a function of stimulus intensity. In terms of repetition rate, all BAEP wave latencies increased and amplitudes decreased with increasing repetition rate. Male rats, compared to females, had significantly longer latencies for several BAEP components and interpeak latencies as well as smaller wave II amplitudes across a broad range of stimulus intensities. Males, compared to females, also had longer BAEP wave IV latencies and I-IV interpeak latencies at a slow stimulus repetition rate (8 clicks/sec) but shorter wave IV and I-IV latencies at a fast repetition rate (120 clicks/sec). These gender-dependent differences indicate that male and female rat BAEP data should not be combined indiscriminantly. Ethanol sedation had a statistically significant effect on the I-IV interpeak latency that was judged to be largely independent of core temperature changes. This finding suggests that while sedatives and anesthetics used to immobilize animals may have apparently minor temperature-independent effects on BAEP latencies, these effects can be statistically significant.     

Brainstem auditory evoked potentials in Guillain-Barré syndrome

Brainstem auditory evoked potentials were abnormal in five of six patients with Guillain-Barré syndrome. The abnormalities imply focal demyelination in the extramedullary portion of the auditory nerve.