Brainstem Auditory-evoked Response Measurements Research Articles

Brainstem auditory-evoked response in healthy African pygmy hedgehogs (Atelerix albiventris).

To evaluate and describe brainstem auditory-evoked response measurements in healthy African pygmy hedgehogs (Atelerix albiventris). Brainstem auditory-evoked response measurements were performed in 12 adult African pygmy hedgehogs (seven males, five females) under general anaesthesia. Waveform morphology was assessed and wave latencies, amplitudes and interpeak latencies calculated. Brainstem auditory-evoked response measurements were successfully performed in both ears from all hedgehogs. Three distinct waves were reproducible in all patients in both ears using a stimulus with an intensity of 90 dB nHL (decibel above normal hearing level). Amplitudes of waves I and V, latencies of waves I, II-III and V and interpeak latencies of waves I-V were calculated at 90 dB for both ears of each animal. This study describes normal brainstem auditory-evoked response morphology and latencies for African pygmy hedgehogs. General anaesthesia is required to perform this neurodiagnostic, given the unique behaviour and anatomy of hedgehogs. This baseline data may be useful for investigating hearing abnormalities and central nervous system disorders in hedgehogs.

Effects of an enrofloxacin-silver sulfadiazine emulsion in the ears of rabbits with perforated tympanic membranes.

To determine whether an enrofloxacin-silver sulfadiazine emulsion (ESS) labeled for treatment of otitis externa in dogs has ototoxic effects in rabbits following myringotomy. 6 healthy adult New Zealand White rabbits. Rabbits were anesthetized for brainstem auditory-evoked response (BAER) tests on day 0. Myringotomy was performed, and BAER testing was repeated. Saline (0.9% NaCl) solution and ESS were then instilled in the left and right middle ears, respectively, and BAER testing was repeated prior to recovery of rabbits from anesthesia. Application of assigned treatments was continued every 12 hours for 7 days, and rabbits were anesthetized for BAER testing on day 8. Rabbits were euthanized, and samples were collected for histologic (6 ears/treatment) and scanning electron microscopic (1 ear/treatment) examination. Most hearing thresholds (11/12 ears) were subjectively increased after myringotomy, with BAER measurements ranging from 30 to 85 dB in both ears. All day 8 hearing thresholds exceeded baseline (premyringotomy) values; results ranged from 30 to 85 dB and 80 to > 95 dB (the upper test limit) in saline solution-treated and ESS-treated ears, respectively. All ESS-treated ears had heterophilic otitis externa, epithelial hyperplasia of the external ear canal, various degrees of mucoperiosteal edema, and periosteal new bone formation on histologic examination. Scanning electron microscopy revealed that most outer hair cells in the ESS-treated ear lacked stereocilia or were absent. Results supported that ESS has ototoxic effects in the middle ear of rabbits. Further research is needed to confirm these findings. Myringotomized laboratory rabbits may be useful to study ototoxicity of drugs used in human medicine.

Brainstem auditory-evoked response (BAER) in client-owned pet ferrets with normal hearing

The objective of this study was to evaluate the feasibility of brainstem auditory-evoked response (BAER) testing in pet ferrets in a clinical setting, and to describe a routine method and...

Use of a hearing loss grading system and an owner‐based hearing questionnaire to assess hearing loss in pet dogs with chronic otitis externa or otitis media

Hearing loss is important when assessing the suitability of dogs with otitis externa/media for medical or surgical therapy. To assess an owner-completed questionnaire as an indicator of hearing loss and a canine hearing loss scoring system in chronic canine otitis. One hundred hospital population dogs referred for chronic otitis investigation. Owners completed a questionnaire to assess their dog's response to common household noises. The presence of otitis externa or media was determined and brainstem auditory-evoked response measurements were performed on each dog. The minimal hearing threshold (MHT) in decibels normal hearing level (dB NHL) was recorded and categorized according to the human World Health Organization grading system into five grades from 0 to 4 with cut-off values of ≤25dB NHL, 26-40dB NHL, 41-60dB NHL, 60-80dB NHL and ≥81dB NHL. The questionnaire correctly determined normal hearing in grade 0 cases, but did not reliably detect unilateral or grade 1 bilateral hearing loss. For dogs with bilateral hearing loss ≥grade 2, questionnaire sensitivity was 83% [24 of 29, 95% confidence interval, (CI) 64-94%] and specificity was 94% (67 of 71, 95% CI 86-98%). Higher grades of hearing loss were significantly associated with the presence of otitis media (P<0.01). The questionnaire may be a useful in-practice screening tool in chronic canine otitis for moderate to severe bilateral hearing deficits (MHT ≥41dB NHL). The hearing loss grading system may help clinicians make therapeutic decisions. Chronic otitis media may be associated with higher grades of hearing loss.

Evaluation of brainstem auditory evoked response audiometry findings in children with tuberculous meningitis at admission

Objective: To determine the characteristics of Brainstem auditory evoked response (BAER) findings in children with tuberculous meningitis (TBM) at admission. Methods: Twenty-seven children with highly probable TBM were admitted to the University Hospital. The control group was 23 healthy, age and sex matched subjects. Brainstem response audiometry recording was performed in all patients and controls. Ninety dB sound pressure level (SPL) was used for comparisons. The main BAER measurements analysed were the I–III, III–V, I–V interpeak intervals. In statistical analysis, t-test for independent groups were performed. At the same time, for interpeak intervals, values exceeding 2.5 standard deviations (S.D.) above the means of the normal controls were considered abnormal. To the result of BAER findings, HL was classified as mild (until 40 dBHL), severe (until 80 dBHL) and total HL (no hearing was detected). Results: The latencies of interpeak intervals (except III–V latency at 10 per s) have significantly prolonged in comparison with controls. Mild HL was detected in four ears. In eight ears, any wave form could not be obtained at 110 dBSPL. Abnormal BAER result was seen in 13 of 54 ears (24%) at the click of 10 per s and five ears (12%) at the click of 50 per s. Conclusion: Abnormal BAER result was seen in 24% of patients with TBM before treatment. Depending on these findings, it can be inferred that hearing impairments must be lower than those values which was detected by BAER during the acute phase of TBM, since the abnormal BAER may be reversible following the illness, returning to normal with recovery.

Brainstem auditory evoked response at five years and prenatal and postnatal blood lead

Previous work from this laboratory demonstrated an association between higher maternal blood lead level at 20 weeks of pregnancy and increased I–V and III–V interpeak intervals in the brainstem auditory evoked response (BAER) recorded in 1-month-old infants. We repeated the BAER measurements with a larger group of children ( n = 100–113) from the same study at 5–7 years. Maternal blood lead level at 20 weeks of pregnancy (geometric mean = 7.7 μg/dl; range 1–30.5 μg/dl) was the only prenatal blood lead level significantly associated with I–V and III–V interpeak interval in a multiple regression model controlling for head circumference and age at time of testing and sex. In contrast to the findings at 1 month of age, interpeak intervals decreased as a linear function of increasing 20-week maternal blood lead. A nonlinear, orthogonal, second-order polynomial model was a significantly better fit to the data than the linear model. The nonlinear model showed I–V and III–V interpeak intervals decreased as blood lead rose from 1 to 8 μg/dl, and then increased as blood lead rose from 8 to 30.5 μg/dl. We hypothesized that the negative linear term was related to lead effect on brainstem auditory pathway length, and that the positive quadratic term was related to neurotoxic lead effect on synaptic transmission or conduction velocity. We found support for the brainstem length interpretation in the data, showing that 6-year-old head circumference in these children significantly decreased with increased maternal 20-week blood lead level. Increasing postnatal blood lead at 12 and 48 months was related only to decreased BAER conduction intervals across the entire blood lead range, suggesting only pathway length effects. Alterations in BAER at this age may indicate that the effect of prenatal lead exposure on the auditory brainstem is permanent, as response latencies reach essentially adult values by 4 years of age.

Use of brainstem auditory-evoked response testing to assess neurologic outcome following near drowning in children.

To determine a correlation between serial brainstem auditory-evoked response measurements and ultimate neurologic outcome in pediatric patients who suffered a cardiac arrest resulting from a submersion accident. Inception cohort, prospective correlational study. A 15-bed pediatric ICU (within a 150-bed tertiary care pediatric hospital) admitting patients of all ages except nonsurgical neonates. All previously normal pediatric patients who suffered a cardiac arrest after a submersion accident. Patients evaluated: 111; patients studied: 89. Patients received serial brainstem auditory-evoked response testing within 6 hrs of resuscitation and then once daily for up to 10 days. Brainstem auditory-evoked response measurements included wave I-V interpeak latency, wave V amplitude, and wave I/V amplitude ratio. Upon discharge, patients were evaluated and classified into one of four neurologic outcome groups: normal, handicapped, vegetative, or dead. Patients classified into the handicapped group exhibited mild neurologic deficits after discharge. Vegetative patients were noninteractive with their environment and required full-time caretaker support. Serial brainstem auditory-evoked response measurements from the four outcome groups were compared with brainstem auditory-evoked response measurements obtained from a group of 39 healthy children of comparable age. Patients who recovered neurologically intact manifested brainstem auditory-evoked response measurements that were similar to controls. Brainstem auditory-evoked response measurements in the handicapped outcome group were also normal after resuscitation but showed significant reduction in wave V amplitudes over the ensuing days. When compared with controls, patients with a vegetative outcome manifested abnormally prolonged wave I-V interpeak latencies, diminished wave V amplitudes, and large-wave I/V amplitude ratios following resuscitation. However, I-V interpeak latencies normalized within 24 hrs after resuscitation. I-V interpeak latencies were no different than controls until hospital day 3, at which time they became significantly prolonged. Patients who were declared brain dead or died from cardiovascular collapse exhibited very abnormal brainstem auditory-evoked response measurements on admission and until death. Wave V could not be detected on admission in 19/31 patients within this group. Brainstem auditory-evoked response testing is useful as an aid in the assessment of neurologic outcome following submersion-induced cardiac arrest. However, standardization of brainstem auditory-evoked response testing and production of normative data are required before this modality can be more widely studied and applied.

Measurement of human BAERs by the maximum length sequence technique.

The traditional brainstem auditory evoked response (BAER) measurement technique (ensemble averaging) is time-consuming and is not acceptable for some time-critical clinical applications. In the paper the application of a pseudorandom binary sequence, the maximum length sequence, to human BAER measurements is examined. This technique permits a faster click rate to stimulate the test subject, and obtains a higher signal-to-noise ratio (SNR) response through deconvolution. When compared with conventional averaging, the method can result in an improved SNR or in faster measurement of BAER. The theory of the technique and the experimental setup are presented, and theoretical analysis on the SNR improvement by this technique against averaging is also given. Actual measurements of BAER on both humans and cats indicate that this technique is effective, especially when the measurement time is not too long, or the number of trials is not too large.

Brainstem auditory-evoked responses with amplification

Brainstem auditory-evoked response (BER) measurements were obtained on adult volunteer subjects who were hearing aid users. The BER's were elicited with click stimulation in several conditions: (1) unaided via earphones, (2) unaided via speaker, and (3) aided via speaker. In the aided condition, subjects adjusted their own hearing aids to their usual comfortable listening level. Aided and unaided audiometric thresholds were also obtained on each subject using pure tones, narrow-band noise, and speech under phones, and using noise and speech in a sound field. Hearing aids were analyzed for frequency response and distortion with a series of inputs and also at user level. Comparisons were made between aided and unaided audiological and BER data. Results indicate that aided BER measurement compared favorably with aided audiological data on cooperative adults and may therefore become useful when applied to hearing aid evaluation procedures for infants and children.