Brainstem auditory evoked potentials with and without increased stimulus rate as diagnostic tool in brainstem minor transient changes

Two clinical groups of patients - 25 with Parkinson's disease and 17 with migraine - were evaluated using brainstem auditory evoked potentials (BAEP) to regular (10/s) and increased (55/s) stimulus rates. Each group of patients had an age-matched control group. The BAEP data were statistically evaluated, comparing the data of migraine patients during and between migraine spells, and the parkinsonian patients before and after L-dopa treatment. We believe that when group data are compared BAEP to an increased stimulus rate is an efficient tool for detecting even minor transient reversible physiologic changes of the brainstem.     

Brainstem auditory evoked potentials with increased stimulus rate in patients suffering from systemic lupus erythematosus

Central nervous system involvement in systemic lupus erythematosus is frequently occult, may be the presenting sign, and is a bad prognostic indicator. At present, there is no reliable, sensitive laboratory test for the evaluation and diagnosis of subclinical central nervous system involvement of the disease. Brainstem auditory evoked potentials with and without increased stimulus rate have been used to diagnose ischemic lesions in the central nervous system. Brainstem auditory evoked potentials, with and without increased stimulus rate, was used to investigate 15 systemic lupus erythematosus patients, 20 normal participants, and 5 patients receiving corticosteroids for bronchial asthma. A significant statistical difference was found in the net effect of increased stimulus rate in comparisons of the systemic lupus erythematosus patients with the normal group. Brainstem auditory evoked potentials, with increased stimulus rate, demonstrated subclinical involvement of the central nervous system in systemic lupus erythematosus, reinforcing the notion that increased stimulus rate measures are sensitive to ischemic changes, in this case, even in neurologically asymptomatic patients.     

Brainstem auditory evoked potentials with speech stimulus in neonates

IntroductionBrainstem auditory evoked potentials in response to complex sounds, such as speech sounds, investigate the neural representation of these sounds at subcortical levels, and faithfully reflect the stimulus characteristics. However, there are few studies that utilize this type of stimulus; for it to be used in clinical practice it is necessary to establish standards of normality through studies performed in different populations.ObjectiveTo analyze the latencies and amplitudes of the waves obtained from the tracings of brainstem auditory evoked potentials using speech stimuli in Brazilian neonates with normal hearing and without auditory risk factors.Methods21 neonates with a mean age of 9 days without risk of hearing loss and with normal results at the neonatal hearing screening were evaluated according to the Joint Committee on Infant Hearing protocols. Auditory evoked potentials were performed with speech stimuli (/da/ syllable) at the intensity of 80 dBNA and the latency and amplitude of the waves obtained were analyzed.ResultsIn the transient portion, we observed a 100% response rate for all analyzable waves (Wave I, Wave III, Wave V and Wave A), and these waves exhibited a latency <10 ms. In the sustained portion, Wave B was identified in 53.12% of subjects; Wave C in 75%; Wave D in 90.62%; Wave E in 96.87%; Wave F in 87.5% and Wave O was identified in 87.5% of subjects. The observed latency of these waves ranged from 11.51 ms to 52.16 ms. Greater similarity was observed for the response latencies, as well as greater amplitude variation in the studied group.ConclusionsAlthough the wave morphology obtained for brainstem evoked potentials with speech stimulation in neonates is quite similar to that of adults, a longer latency and greater variation in amplitude were observed in the waves analyzed.     

Brainstem auditory evoked response in presbyacusis

Brainstem auditory evoked responses (BAER) were studied in twenty elderly patients with presbyacusis and results were compared with twenty age and sex matched controls. Absolute latency of wave-I was significantly delayed, resulting in significant shortening of interpeak interval of I–III waves and was consistent with cochlear sensorineural hearing losses. No evidence of retrocochlear involvement was observed.     

Brainstem auditory evoked potentials in children with lead exposure

IntroductionEarlier studies have demonstrated an auditory effect of lead exposure in children, but information on the effects of low chronic exposures needs to be further elucidated.ObjectiveTo investigate the effect of low chronic exposures of the auditory system in children with a history of low blood lead levels, using an auditory electrophysiological test.MethodsContemporary cross-sectional cohort. Study participants underwent tympanometry, pure tone and speech audiometry, transient evoked otoacoustic emissions, and brainstem auditory evoked potentials, with blood lead monitoring over a period of 35.5 months. The study included 130 children, with ages ranging from 18 months to 14 years, 5 months (mean age 6 years, 8 months ± 3 years, 2 months).ResultsThe mean time-integrated cumulative blood lead index was 12 μg/dL (SD ± 5.7, range: 2.433). All participants had hearing thresholds equal to or below 20 dBHL and normal amplitudes of transient evoked otoacoustic emissions. No association was found between the absolute latencies of waves I, III, and V, the interpeak latencies I–III, III–V, and I–V, and the cumulative lead values.ConclusionNo evidence of toxic effects from chronic low lead exposures was observed on the auditory function of children living in a lead contaminated area.     

Brainstem and middle latency auditory evoked responses in rabbits with halothane anaesthesia

The effects of different concentrations of halothane (0.5, 1 and 1.5%) in brainstem and middle latency auditory evoked responses were studied in 14 adult rabbits. The animals were firstly curarized, tracheostomized and ventilated mechanically. Various recording were made under these conditions for control purposes. During the experiment, arterial pressure, temperature, arterial concentrations of O2, CO2 and pH were monitored. Halothane produce an increase in latency a decrease in amplitude and at higher concentrations even abolished the later waves of middle latency auditory evoked responses. Brainstem potentials are stable, but slight changes in latency were observed at high concentrations (1.5%). Modifications of these potentials as a result of the different concentrations of this anaesthetic in relation with the recordings obtained in the animals curarized without anaesthesia are discussed and the results compared with previous reports in humans.     

Brainstem auditory evoked potentials correlate with morphological changes in Gunn rat pups.

The relationship of brainstem structure and function in bilirubin encephalopathy is incompletely understood. The present experiments compare quantitative measures of brainstem structures with brainstem auditory evoked potentials (BAEPs) in infant jaundiced (jj) and nonjaundiced (Nj) Gunn rats. Ten jj's from 4 litters were injected with sulfadimethoxine at 11-12 days of age to raise their brain bilirubin concentration. Littermate controls were jj's given saline, and Nj's given sulfadimethoxine or saline. At 15-17 days of age BAEPs were recorded, and rats were prepared for histological examination, as was reported in the previous paper (Conlee and Shapiro, 1991). Significant differences between groups were seen for BAEP wave I latency (P = 0.002). I-II interwave interval (P = 0.001), and amplitudes of waves I, II, III, and IV (each P less than 0.0005) due to increased latencies and decreased amplitudes in the jj-sulfa group. Animals with the most severe BAEP abnormalities had the most severe histological abnormalities. Cochlear nucleus volume had a positive linear correlation with the amplitude of BAEP waves I, II, and IV, and an inverse correlation with wave I latency and I-II interwave interval (P less than or equal to 0.001). The highest correlations were BAEP I-II interwave interval and amplitude of waves I and II with cochlear nucleus volume (r = -0.78, 0.71 and 0.70, respectively, P less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Brainstem auditory evoked response in the ferret (Mustela putorius)

The effect of click intensity, repetition rate and binaural interaction on the brainstem auditory evoked response (BAER) was examined in sixteen pigmented adult male ferrets. Potentials were recorded from platinum needle electrodes inserted over the vertex and left and right mastoids. Square waves, 100 microseconds in duration, were transduced by earphones enclosed in an assembly designed to fit securely over the ferret's external ear. The BAER in the ferret consists of four prominent vertex-positive peaks (P1-P4) and a fifth peak of smaller amplitude and more variable latency. The mean latencies of P1-P4 at 104 dB peak SPL were 0.96, 1.83, 2.75 and 3.62 ms. Reducing intensity over a 70 dB range resulted in a reduction in amplitude and a corresponding increase in latency ranging between 0.57 and 0.67 ms. Also, increasing click repetition rate resulted in a reduction in amplitude and an increase in latency. With intensity fixed at 104 dB peak SPL comparison of latencies at 10 and 50/s showed a mean increase of 20, 50, 60 and 80 microseconds for P1-P4, respectively. The effect of binaural interaction on the BAER was examined using the procedure of Dobie and Berlin (1979); the response evoked by binaural stimulation was subtracted from the summed left and right monaural responses to obtain a binaural interaction component. Binaural interaction in the ferret gave rise to a distinct vertex-negative wave with a latency similar to P4. An increase in click intensity over a 70 dB range resulted in a monotonic increase in amplitude and a decrease in latency of the binaural interaction component.     

青年急性耳鸣高刺激率ABR的检测及临床意义

目的研究高刺激率听觉脑干反应（Auditory brainstem response,ABR）检测对青年急性耳鸣的临床意义。方法选取青年急性耳鸣58耳与正常青年44耳,分别进行高、低刺激率ABR检测,比较波Ⅰ、Ⅲ、Ⅴ的潜伏期（peaklatency,PL）和Ⅰ～Ⅲ、Ⅲ～Ⅴ和Ⅰ～Ⅴ峰间潜伏期（interpeak latency,IPL）及两种刺激速率PL差值（ΔPL）、IPL差值（ΔIPL）。结果采用51.1次/s与11.1次/s的波PL及IPL的差值作为分析参数：耳鸣组波ⅠPL差值较正常组缩短,有统计学意义（P〈0.05）;Ⅰ～ⅤIPL差值较正常组延长,差异具有显著性（P〈0.01）。正常组与耳鸣组高、低刺激率ABRⅠ～ⅤIPL差值〉0.272ms的耳数分别为1耳和28耳。结论高刺激率ABR较常规ABR对青年急性耳鸣的检测更为敏感,可作为耳鸣患者的一种临床检查方法。     

Brainstem auditory evoked response sensitivity: comparison with other neurologic tests in the detection of retrocochlear lesions

Brainstem auditory evoked response (BAER) tests were obtained in 3 patients with suspected retrocochlear lesions. Subsequently, CT scans and the surgical procedure demonstrated tumors of about the same size (2 cm) in the cerebellopontine angle. One was an VIIIth-nerve schwannoma, one a meningioma, and one a VIIth-nerve neuroma. BAER recordings were analyzed with results of other tests: conventional audiometry, stapedius reflex measurements and electronystagmography (ENG). A striking finding was a normal BAER in the patient with the VIIIth-nerve schwannoma. ENG recordings in this case showed ipsilateral impairment of optokinetic nystagmus. The BAER was abnormal in the other 2 patients. A consistent abnormality for the 3 patients was absence of stapedius reflex in the ear in question. This study disclosed the advantage of utilizing a battery of tests in the investigation of retrocochlear lesions. The ENG recordings should include evaluation of the vestibulo-oculomotor pathways.     

Time-intensity trading in the late auditory evoked potential.

The present study investigated physiological correlates of the time-intensity trading relationship in late components (N1, P2) of the auditory evoked potential. Late-potential and behavioral thresholds were estimated in five normal-hearing, young adult participants for 1000- and 4000-Hz tone bursts having durations of 8, 16, 32, 64, and 128 ms. The results showed that late-potential thresholds decreased by an average of 24 dB for 1000-Hz conditions and 18 dB for 4000-Hz conditions. Behavioral thresholds also improved by about 22 dB and 18 dB for 1000-Hz and 4000-Hz conditions, respectively. The slope of improvement for both late-potential and behavioral thresholds was on the order of -4 to -6 dB per doubling of stimulus duration, depending on stimulus frequency. Stimulus duration also influenced latency and amplitude measures of the N1 and P2 components such that response latency decreased and amplitude increased as stimulus duration increased. The present results demonstrate a time-intensity trading relationship in components of the late potentials that is consistent with previous psychophysical and physiological data.     

Frequency and age-dependent auditory evoked potential thresholds in infants

Auditory evoked-potential thresholds to 0.5, 4.0 and 10.0 kHz tone pips were measured in 40 normal infants 2–28 wks old and 14 normal hearing adults. Thresholds to 500 Hz tone pips were based upon the steady-state, 40 Hz. evoked potential. Thresholds to 4.0 and 10.0 kHz tone pips were based upon the brainstem response. Stimulus intensity was varied in 5-dB steps for threshold search. The greatest difference between infant and adult thresholds occurred at 4.0 kHz. The magnitude of this difference decreased with age; however, differences were still significant up to 28 wks of age. No significant differences were seen at 500 Hz. To the 10.0 kHz stimulus only the youngest (2–4 wk) infants had thresholds that were significantly higher than adults. The reasons proposed to explain these results are complex interactions between immaturity of the conductive mechanism, brainstem pathways, and possibly the cochlea.     

Brainstem auditory evoked potentials after irradiation of nasopharyngeal carcinoma--report on two cases with myelopathy of the brainstem

Brainstem auditory evoked potentials (BAEP) were recorded in two patients with nasopharyngeal carcinoma (NPC) irradiated 14 and three years ago respectively and compared with 15 healthy controls. The patients had features of post-irradiation myelopathy of the brainstem with reduced gag reflex, unilateral vocal cord paralysis and fasciculation of the tongue. The first patient had a blind left eye. The second patient had quadriparesis. All ears revealed post-irradiation otitis media changes and mixed deafness. BAEP was not recognizable in the left ear of the first patient and was normal in the left ear of the second patient. Simultaneous electrocochleogram and BAEP were recorded from the right ear of the first case. The wave I-V latency interval were prolonged in both right ears. In the absence of local recurrence and brain secondaries, these BAEP changes are attributed to the post-irradiation myelopathy of brainstem.