Clinical significance of electrically evoked auditory brainstem response

Electrically evoked auditory brainstem responses (EABR) were recorded in 31 postlingually deafened adults, who had recently received cochlear implants (mini-system, Cochlear Ltd). The wave consisted of three distinct positive peaks labeled P1, P2, and P3 with latency of 1.35 (+/- 0.14), 2.17 (+/- 0.18) and 4.08 (+/- 0.31) ms, respectively. The P3 threshold (EABR-T) and slope (EABR-S) were 0.9 (+/- 0.47) mA and 0.6 (+/- 0.28) muv/mA, respectively. The relationships between the EABR parameters (EABR T and -S of the P3 wave) and age, duration of deafness, promontory test and subjective response (T and C-level) were investigated. The scattergram showed a strong negative linear relationship between EABR-S and subjective T-level. This finding suggests that EABR-S is good measure of postoperative perception.     

Infant temperament and the brainstem auditory evoked response in later childhood.

Brainstern auditory evoked responses (BAERs) were evaluated on 10–12-year-old children (N?=?56) who had been classified as high or low reactive to unfamiliar stimuli at 4 months of age. BAER measurement was selected because high reactive infants tend to become inhibited or fearful young children, and adult introverts have a faster latency to wave V of the BAER than do extroverts. Children previously classified as high reactive at 4 months had larger wave V components than did low reactive children, a finding that possibly suggests greater excitability in projections to the inferior cofliculus. The fact that a fundamental feature of brainstem activity differentiated preadolescent children belonging to two early temperamental groups supports the value of gathering physiological data in temperament research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of noise burst rise time and level on the human brainstem auditory evoked response

An experiment was conducted to examine the effects of noise burst rise time and level on the human BAER. Noise burst levels included 15, 30, 45 and 60 dB nHL, with linear rise times of 0, 0.5, 1.25 and 2.5 ms. With increasing noise burst level, there is a decrease in wave V latency and an increase in peak amplitude. With increasing noise burst rise time, there is an increase in wave V latency and a decrease in wave V amplitude. The slope of the latency/intensity function increases with increasing rise time. The slope of the latency/rise time function increases with decreasing noise burst level. The change in wave V latency associated with changing rise time is less than the change in rise time for all experimental conditions.     

Brainstem auditory evoked potentials during brainstem ischemia and reperfusion in gerbils

To evaluate the reversibility of neural function in the brainstem following ischemia, we investigated the effect of transient brainstem ischemia on the brainstem auditory evoked potential in gerbils. Brainstem ischemia was produced by bilateral extracranial occlusion of vertebral arteries. Local cerebral blood flow was measured by quantitative autoradiography after 5 min of ischemia and was reduced to less than 3 ml/100 g per min in the pons and lower midbrain, indicating severe and reproducible brainstem ischemia. During brainstem ischemia, brainstem auditory evoked potential waveforms disappeared completely. After a brief ischemic insult (5 min), all four brainstem auditory evoked potential components recovered to normal. After longer ischemic insults (10-30 min), brainstem auditory evoked potential components never recovered to normal. Microtubule-associated protein 2 immunoreactivity revealed differential vulnerability of the acoustic relay nuclei in the brainstem. Neurons in the lateral lemniscus were most vulnerable, followed in order by neurons in the trapezoid body, the superior olive and the cochlear nucleus. We also demonstrated a close relationship between the reversibility of ischemia-induced changes on brainstem auditory evoked potential and ischemic lesions of these relay nuclei. These data may be useful for evaluating the therapeutic window of thrombolytic therapy during acute vertebrobasilar occlusion.     

Contralateral evoked brainstem auditory potentials as an indicator of intraoperative brainstem manipulation in cerebellopontine angle tumors

Brainstem auditory evoked potentials (BAEP) were studied during operations to remove acoustic tumors using the retromastoid approach. BAEP were elicited from the side contralateral to the tumor, and changes in the latencies of peaks III and V of the BAEP were compared with changes in cardiovascular parameters throughout the operation. When the changes in the determined cardiovascular parameters were related to surgical manipulations, the related changes in the latencies of peaks III and V of the BAEP were more consistent than the changes in the cardiovascular parameters and they tended to occur earlier than the changes noted in the cardiovascular parameters.     

Reversible brainstem auditory evoked potential abnormalities in jaundiced Gunn rats given sulfonamide

Renal transplantation therapy performed for amyloid nephropathy is controversial because of the fatal effects of the disease. Amyloidosis is a relatively frequent disease and is generally associated with familial Mediterranean fever (FMF) in Turkey. Renal transplantation in the treatment of amyloid nephropathy started in January 1985. Till now, 18 (3.2%) renal transplantations have been performed on patients who had amyloid nephropathy. The mean follow-up period was 34.6 months. Fourteen renal grafts still function well (creatinine: 1-3.2 mg/dL). The overall 1-year patient and graft survival rates were 88.9% and 83.0%, respectively. These rates are not statistically different from renal transplantations done for other cases of renal failure. Therefore, patients with end-stage renal failure due to amyloidosis can be considered as appropriate candidates for renal transplantation.     

Effects of acute brainstem compression on auditory brainstem response in the guinea pig

BACKGROUND: The purpose of this study was to establish the norm for parameters of auditory brainstem response (ABR) in the guinea pig and to investigate if acute brainstem compression results in significant changes to these parameters. METHODS: Thirty-six guinea pigs with positive Preyer's reflex were anesthetized. A craniectomy was performed to remove the right occipital bone and the dura mater was opened to expose the brain, cerebellum and cerebellopontine angle (CPA). A small inflatable balloon was placed into the CPA precisely and slowly. ABR was recorded before incision of the skin as a baseline value, after placement and after inflation of the balloon with water at 0.1-ml intervals. RESULTS: Five stable peaks were recorded in 27 experimental animals. When the balloon was inflated with 0.1 ml water, the absolute latency (AL) of peaks IV and V and the interpeak latency (IPL) of peaks III and IV, and IV and V were prolonged. The amplitude ratios (AR) of peaks II, III, IV and V to peak I decreased. Inflation of the balloon with 0.2 ml of water caused further elongation of ALs of peaks IV and V and decreases in each AR. When the balloon volume increased to 0.3 ml, peak V became unrecognizable and peaks III and IV showed significant elongation of AL; peaks I and II did not show significant change in ALs. Further increase of the balloon volume to 0.4 ml resulted in disappearance of peaks III, IV and V; AL of peak II was also elongated. However, the amplitude and AL of peak I remained unchanged. Similar changes were observed in IPLs. CONCLUSIONS: This study establishes the norm of parameters of ABR in guinea pigs and demonstrates that acute brainstem compression causes elongation of ALs and IPLs of peaks II, III, IV and V. This suggests that peaks II, III, IV and V come from the brainstem and that peak I is not generated from the brainstem in the guinea pig.     

Methods of sedation for auditory brainstem response testing

The unicellular protozoan parasite, Crithidia luciliae, responded to osmotic swelling by undergoing a regulatory volume decrease. This process was accompanied by the efflux of amino acids (predominantly alanine, proline and glycine). The relative loss of the electroneutral amino acids proline, valine, alanine and glycine was greater than that for the anionic amino acid, glutamate; there was negligible loss of the cationic amino acids, lysine, arginine and ornithine. The characteristics of amino acid release were investigated using a radiolabeled form of the nonmetabolized alanine analogue alpha-aminoisobutyrate. alpha-Aminoisobutyrate efflux was activated within a few seconds of a reduction of the osmolality, and inactivated rapidly (again within a few seconds) on restoration of isotonicity. The initial rate of efflux of alpha-aminoisobutyrate from cells in hypotonic medium was unaffected by the extracellular amino acid concentration. Hypotonically activated alpha-aminoisobutyrate efflux (as well as the associated regulatory volume decrease) was inhibited by the sulfhydryl reagent N-ethylmaleimide but was not inhibited by a range of anion transport blockers. As in the efflux experiments, unidirectional influx rates for alpha-aminoisobutyrate increased markedly following reduction of the osmolality, consistent with the swelling-activated amino acid release mechanism allowing the flux of solutes in both directions. Hypotonically activated alpha-aminoisobutyrate influx showed no tendency to saturate up to an extracellular concentration of 50 mM. The functional characteristics of the amino acid release mechanism are those of a channel, with a preference for electroneutral and anionic amino acids over cationic amino acids. However, the pharmacology of the system differs from that of the anion-selective channels that are thought to mediate the volume-regulatory efflux of organic osmolytes from vertebrate cells.     

Adaptive denoising and multiscale detection of the V wave in brainstem auditory evoked potentials

This paper describes a wavelet-transform-based system for the V wave identification in brainstem auditory evoked potentials (BAEP). The system combines signal denoising and rule-based localization modules. The signal denoising module has the potential of effective noise reduction after signal averaging. It analyses adaptively the evolution of the wavelet transform maxima across scales. The singularities of the signal create wavelet maxima with different properties from those of the induced noise. A non-linear filtering process implemented with a neural network extracts out the noise-induced maxima. The filtered wavelet details are subsequently analysed by the rule-based localization module for the automatic identification of the V wave. In the first phase, it implements a set of statistical observations as well as heuristic criteria used by human experts in order to classify the IV-V complex. At the second phase, using a multiscale focusing algorithm, the IV and V waves are positioned on the BAEP signal. Our experiments revealed that the system provides accurate results even for signals exhibiting unclear IV-V complexes.     

Isochronic mapping of the auditory brainstem response: normative results

Isochronic mapping involves recording multi-channel evoked potentials from scalp electrodes and plotting contours of peak latencies. In this study, auditory brainstem responses were recorded from 20 electrode sites for left, right and binaural stimulation of each ear of 10 male and 10 female, normally hearing, young adults. Analysis of the data showed that the stimulus parameters of intensity, polarity and rate had no significant effect on the maps. On monaural stimulation, wave V was recorded first at the contralateral mastoid and ipsilaterally frontally and last at the ipsilateral mastoid some 350, mu s later. Binaural stimulation gave a symmetrical map, with wave V recorded first frontally and last at the occiput. In contrast, wave III was recorded first ipsilaterally and frontally and last at the contralateral mastoid. Wave II was recorded first at the rear of the contralateral mastoid and last forward of the ipsilateral mastoid. Comparisons between these results and human physiological studies are in agreement for waves V and III but do not support the concept of the VIIth nerve alone as the generator for wave II. These results suggest that this technique is a potentially useful diagnostic tool and it is intended to evaluate it by testing patients with a range of sensory, peripheral-neural and central-neural pathologies.     

Developmental exposure to Aroclor 1254 produces low-frequency alterations in adult rat brainstem auditory evoked responses

Developmental exposure of Long-Evans rats to 0, 1, 4, or 8 mg/kg/day Aroclor 1254 (A1254) from Gestational Day 6 through Postnatal Day 21 produces an elevated behavioral threshold for a 1-kHz tone. Brainstem auditory evoked responses (BAERs) were assessed in a subset of these animals (about 1 year old) using filtered clicks at 1 (65 and 80 dB SPL), 4 (60 and 80 dB SPL), 16 (40 and 80 dB SPL), and 32 (40 and 80 dB SPL) kHz. Aroclor 1254 decreased BAER amplitudes at 1 and 4 kHz, but not at 16 or 32 kHz. A dose-related decrease in the baseline-to-peak P1A amplitude was observed for the 1-kHz (80-dB) stimulus. Doses of 1, 4, or 8 mg/kg/day A1254 decreased the peak-to-peak amplitude of both P1AN1 and P1BN1 for a 1-kHz (80-dB) stimulus. Doses of 4 and 8 mg/kg/day A1254 decreased the peak-to-peak amplitude of N1P2 and P2N2 for a 4-kHz (60-dB) or 1-kHz (80-dB) stimulus. At 8 mg/kg/day, A1254 also increased the latency of peak P4 at 1 kHz (65 dB). The decreases in peak P1A amplitudes are consistent with a dysfunction of the cochlea and/or auditory nerve. Together, the data confirm that developmental exposure of rats to A1254 produces a permanent low- to mid-frequency auditory dysfunction and suggest a cochlear and/or auditory nerve site of action.     

Value of auditory evoked potentials of the cerebral brainstem in the diagnosis of retrocochlear tumors

The use of auditory brainstem response (ABR) in the diagnosis of retrocochlear tumoral pathology has been established for years, but the development of magnetic resonance imaging for the same purpose calls for a review of the value of this method. We studied 200 ABR records made to exclude pathology. The results indicate that ABR is useful as a screening method in this type of pathology when carried out in a population with any auditory symptom, although it was not very suggestive. In most positive tests, the presence of pathology is not confirmed.     

Effect of organophosphorus compound intoxication on auditory brainstem response in mini pigs

Marketing analysis is a means of identifying consumer satisfaction, thus providing a means of exploiting weaknesses in competitors. As part of a graduate midwifery programme a small study was undertaken analysing marketing activities used by one competitor provider of maternity care services. The Marketing mix, Ansoff matrix and Gap analysis were the marketing tools used. Recommendations to midwifery service providers suggest using market research to identify consumer expectations and explore areas of both satisfaction and dissatisfaction.     

MRI and brainstem auditory evoked potential evidence of eighth cranial nerve involvement in multiple sclerosis

An MS patient experienced sudden hearing loss. Brainstem auditory evoked potentials, previously normal, showed substantial abnormalities that suggested the impairment of the distal part of the acoustic nerve. MRI detected a small hyperintense lesion along the acoustic nerve; the lesion decreased in size and then disappeared after steroid treatment. This demonstrates that a demyelinating lesion in the distal tract of the eighth cranial nerve may cause an acute hearing loss in MS.     

Use of contralateral masking in the measurement of the auditory brainstem response

In the first portion of this study, the effects of two levels of contralateral masking on the auditory brainstem response (ABR) were investigated in 10 normal-hearing subjects. No significant changes were observed in the mean latency-intensity functions or the mean amplitude-intensity functions of this group of subjects when noise of various levels was added to the nontest ear. In the second portion of this study, ABRs were also recorded from the poorer ear of four subjects with a profound unilateral sensorineural hearing loss. Results from the latter group revealed a crossed-over wave V in all cases when the stimulus was delivered to the poorer ear and the nontest (better) ear was not masked. Contralateral masking obliterated this "crossed ABR" in all four unilaterally impaired subjects. These results provide support for the use of contralateral masking when recording from the poorer ear of subjects having asymmetrical hearing loss.     

Development of an expert system for pediatric auditory brainstem response interpretation

Expert systems are computer programs which incorporate artificial intelligence technology and are created to emulate the decision-making abilities of human experts. The advantage of such systems lies in their ability to capture and model expert problem solving knowledge in a domain and make it available to an unlimited number of consumers in an economic and efficient way. The purpose of this project was to develop an expert system to interpret infant auditory brainstem response data as entered by the user. The resulting system provides diagnostic conclusions regarding hearing status, type of hearing loss, and brainstem function at an accuracy level equal to that of a human expert.     

Test-retest variability of the auditory brainstem response to bone-conducted clicks in newborn infants

1. The effects of adenosine and its analogues on actin polymerization in human polymorphonuclear leucocytes (PMN) induced by three different chemotactic stimulants, platelet-activating factor (PAF), N-formyl-methionyl-leucyl-phenylalanine (FMLP) and an activated fragment of C5 (C5a) were investigated. 2. Adenosine and its analogues inhibited the actin polymerization induced by these three agents in a concentration-dependent manner and theophylline, a competitive antagonist at adenosine receptors, abolished these inhibitory effects. 3. The adenosine analogue 5'-N-ethylcarboxamideadenosine (NECA) was a more potent inhibitor of actin polymerization than either L-N6-phenylisopropyladenosine (PIA) or adenosine itself; the rank order of potency of these agonists was characteristic of adenosine A2 receptors. 4. Adenosine deaminase (ADA) abolished the inhibitory effect of adenosine and augmented PAF-induced actin polymerization. 5. It was concluded that, at physiological concentrations, adenosine inhibits actin polymerization in PMN via activation of PMN surface membrane adenosine A2 receptors and thus modulates chemotactic stimulus-induced PMN motility.     

Recovery from pre-operative sedation with clonidine--brain stem auditory evoked response

Diagnostic laparoscopy has been an integral part of our surgical practice for over 4 years. Between 1988-1992, 100 diagnostic laparoscopies have been performed in this institution without mortality. We have found the procedure to be particularly useful in the following situation: 1) Hepatobiliary disease where it is used in conjunction with targeted liver biopsy. 2) Acute emergency cases. These include the diagnosis of acute peritonitis, abdominal trauma and in patients with suspected mesenteric ischaemia. 3) In the staging of intra-abdominal malignancy especially gastric, oesophageal, colonic, peritoneal and pancreatic neoplasms.     

A parametric study of the N40 auditory evoked response in rats

BACKGROUND: The N40 auditory evoked potential (EP) in rats is used to study "sensory gating." Our first goal was to compare the effects of systematically varying the characteristics of the pairs of clicks (S1-S2), on the degree of attenuation of the responses to S2 stimuli. A second goal was to examine the effects of changing S2 stimuli on the degree of attenuation of the responses to the deviant stimulus. METHODS: The N40 EP was recorded from 10 rats in eight identical-pair conditions and from 11 rats in two paradigms: nonidentical pairs and short trains of identical stimuli followed by a deviant stimulus. RESULTS: In eight identical-pair conditions changing stimulus duration, intensity, or frequency had no effect on the degree of attenuation of S2 responses. Changing S2 stimulus or presenting a deviant stimulus following a train of identical stimuli had a significant effect on the degree of attenuation of the response to the deviant stimulus. CONCLUSIONS: We conclude that the rat N40 EP is sensitive to stimulus change and can contribute to the study of both habituation and dishabituation mechanisms of "sensory gating."