Auditory brain stem evoked responses to bone-conducted signals

Improved Bone Conduction Hearing After Middle Ear Surgery: Investigation of the Improvement Mechanism

OBJECTIVES

When performing middle ear operations, such as ossiculoplasty or stapes surgery, patients and surgeons expect an improvement in air conduction (AC) hearing, but generally not in bone conduction (BC). However, BC improvement has often been observed after surgery, and the present study investigated this phenomenon.

METHODS

We reviewed the preoperative and postoperative surgical outcomes of 583 patients who underwent middle ear surgery. BC improvement was defined as a BC threshold decrease of >15 dB at two or more frequencies. Subjects in group A underwent staged ossiculoplasty after canal wall up mastoidectomy (CWUM), group B underwent staged ossiculoplasty after canal wall down mastoidectomy (CWDM), group C underwent ossiculoplasty only (thus, they had no prior history of CWUM or CWDM), and group D received stapes surgery. We created a hypothetical circuit model to explain this phenomenon.

RESULTS

BC improvement was detected in 12.8% of group A, 9.1% of group B, and 8.5% of group C. The improvement was more pronounced in group D (27.0%). A larger gain in AC hearing was weakly correlated with greater BC improvement (Pearson's r=0.395 in group A, P<0.001; r=0.375 in group B, P<0.001; r=0.296 in group C, P<0.001; r=0.422 in group D, P=0.009). Notably, patients with otosclerosis even experienced postoperative BC improvements as large as 10.0 dB, from a mean value of 30.3 dB (standard error [SE], 3.2) preoperatively to 20.3 dB (SE, 3.2) postoperatively, at 1,000 Hz, as well as an improvement of 9.2 dB at 2,000 Hz, from 37.8 dB (SE, 2.6) to 28.6 dB (SE, 3.1).

CONCLUSION

BC improvement may be explained by a hypothetical circuit model applying the third window theory. Surgeons should keep in mind the possibility of BC improvement when making a management plan.

Round Window Membrane Motion Induced by Bone Conduction Stimulation at Different Excitation Sites: Methodology of Measurement and Data Analysis in Cadaver Study

OBJECTIVES

The aim of this study was to investigate the following: (1) the vibration pattern of the round window (RW) membrane in human cadavers during air (AC) and bone conduction (BC) stimulation at different excitation sites; (2) the effect of the stimulation on the fluid volume displacement (VD) at the RW and compare the VD between BC and AC stimulation procedures; (3) the effectiveness of cochlear stimulation by the bone implant at different excitation sites.

DESIGN

The RW membrane vibrations were measured by using a commercial scanning laser Doppler vibrometer. The RW vibration amplitude was recorded at 69 measurement points evenly distributed in the measurement field covering the entire surface of the RW membrane and a part of the surrounding bony surface. RW vibration was induced first with AC and then with BC stimulation through an implant positioned at two sites. The first site was on the skull surface at the squamous part of the temporal bone (implant no. 1), a place typical for bone-anchored hearing aids. The second site was close to the cochlea at the bone forming the ampulla of the lateral semicircular canal (implant no. 2). The displacement amplitude (dP) of the point P on the promontory was determined and used to calculate the relative displacement (drRW) of points on the RW membrane, drRW = dRW - dP. VD parameter was used to analyze the effectiveness of cochlear stimulation by the bone implant screwed at different excitation sites.

RESULTS

RW membrane displacement amplitude of the central part of the RW was similar for AC and BC implant no. 1 stimulation, and for BC implant no. 2 much larger for frequency range >1 kHz. BC implant no. 2 causes a larger displacement amplitude of peripheral parts of the RW and the promontory than AC and BC implant no. 1, and BC implant no. 1 causes larger than AC stimulation. The effect of BC stimulation exceeds that of AC with identical intensity, and that the closer BC stimulation to the otic capsule, the more effective this stimulation is. A significant decrease in the value of VD at the RW is observed for frequencies >2 kHz for both AC and BC stimulation with BC at both locations of the titanium implant placement. For frequencies >1 kHz, BC implant no. 2 leads to a significantly larger VD at the RW compared to BC implant no. 1. Thus, the closer to the otic capsule the BC stimulation is located, the more effective it is.

CONCLUSIONS

Experimental conditions allow for an effective acoustic stimulation of the inner ear by an implant screwed to the osseous otic capsule. The mechanical effect of BC stimulation with a titanium implant placed in the bone of the ampulla of the lateral semicircular canal significantly exceeds the effect of an identical stimulation with an implant placed in the temporal squama at a conventional site for an implant anchored in the bone. The developed research method requires the implementation on a larger number of temporal bones in order to obtain data concerning interindividual variability of the observed mechanical phenomena.

Normalization of Bone Conduction Auditory Brainstem Evoked Responses in Normal Hearing Individuals

OBJECTIVES

Auditory brainstem responses (ABR) are used to evaluate the peripheral and central functions of the auditory tract. Air and bone-conduction auditory stimuli are used to evaluate the type and degree of hearing loss. The wave latencies and interpeak latencies (IPLs) are the important diagnostic data in ABR tests. Gender and age of the patients are some of the factors affecting these latencies. This study investigated the effects of age and gender on the wave and IPLs of bone-conduction ABR.

MATERIALS AND METHODS

One hundred healthy individuals (50 women and 50 men) aged between 10 and 60 years were enrolled into this study, and both ears of all subjects (200 ears total) were included in the assessments. Based on their age, the subjects were equally divided into five groups, and each group consisted of 10 men and 10 women.

RESULTS

The findings showed a significant difference in wave latencies and IPLs between the two genders (p<0.05). Depending on stimulus intensity, wave latencies also showed statistically significant differences between the age groups (p<0.05). However, no significant difference was noted between the age groups regarding IPLs.

CONCLUSION

Normative values that covered wave latencies and IPLs evoked at stimulus intensities of 50, 30, and 10 dB nHL were established for the clinical use and use as a reference for the bone-conduction ABR testing procedure.

Ultrasonic Neuromodulation Causes Widespread Cortical Activation via an Indirect Auditory Mechanism

Ultrasound has received widespread attention as an emerging technology for targeted, non-invasive neuromodulation based on its ability to evoke electrophysiological and motor responses in animals. However, little is known about the spatiotemporal pattern of ultrasound-induced brain activity that could drive these responses. Here, we address this question by combining focused ultrasound with wide-field optical imaging of calcium signals in transgenic mice. Surprisingly, we find cortical activity patterns consistent with indirect activation of auditory pathways rather than direct neuromodulation at the ultrasound focus. Ultrasound-induced activity is similar to that evoked by audible sound. Furthermore, both ultrasound and audible sound elicit motor responses consistent with a startle reflex, with both responses reduced by chemical deafening. These findings reveal an indirect auditory mechanism for ultrasound-induced cortical activity and movement requiring careful consideration in future development of ultrasonic neuromodulation as a tool in neuroscience research.

Auditory Brainstem Response Thresholds to Air- and Bone-Conducted CE-Chirps in Neonates and Adults

PURPOSE

The purpose of this study was to compare auditory brainstem response (ABR) thresholds to air- and bone-conducted CE-Chirps in neonates and adults.

METHOD

Thirty-two neonates with no physical or neurologic challenges and 20 adults with normal hearing participated. ABRs were acquired with a starting intensity of 30 dB normal hearing level (nHL). The lowest stimulus intensity level at which a wave V was identifiable and replicable was considered the ABR threshold.

RESULTS

ABR thresholds to air-conducted CE-Chirps were 9.8 dB nHL for neonates and adults. ABR thresholds to bone-conducted CE-Chirps were 3.8 and 13.8 dB nHL for neonates and adults, respectively. The difference in ABR thresholds to bone-conducted CE-Chirps was significantly different (p < .0001, ηp2 = .45). Adults had significantly larger wave V amplitudes to air- (p < .0001, ηp2 = .50) and bone-conducted (p = .013, ηp2 = .15) CE-Chirps at a stimulus intensity of 30 dB nHL. At the same intensity, adults evidenced significantly shorter wave V latencies (p < .0001, ηp2 = .49) only with air-conducted CE-chirps.

CONCLUSION

The difference in ABR thresholds and wave V latencies to air- and bone-conducted CE-Chirps between neonates and adults may be attributed to a disparity in effective signal delivery to the cochlea.

Potencial evocado auditivo de tronco encefálico por condução óssea: uma revisão integrativa

O objetivo deste estudo foi de realizar uma revisão de forma integrativa sobre os procedimentos utilizados nos critérios de aquisição do exame de Potenciais Evocados Auditivos de Tronco Encefálico por condução óssea com fins ao auxílio no diagnóstico de problemas auditivos. Foi realizada uma busca nas seguintes bases de dados: Literatura Latino-Americana e do Caribe em Ciências da Saúde (Lilacs), Medical Literature Analysis and Retrieval System Online (Medline) e Scientific Eletronic Library Online (SciELO). Utilizaram-se as seguintes palavras-chave: Potencial Evocado Auditivo, Eletrofisiologia e Condução Óssea, encontrados por meio de Descritores em Ciências da Saúde (DeCS). Os resultados apresentados são referentes aos 35 estudos selecionados. A maioria dos estudos optou pelo uso do estímulo clique, com transdutores por condução aérea os fones supra-aurais, como o TDH-39, para o estímulo por condução óssea, o vibrador Radioear B-71, com pressão de 425+/-25g. Observou-se que a mastoide foi à região onde mais se posicionou mais o vibrador ósseo. A maioria dos estudos refere usar polaridade alternada, com taxa de apresentação diversificada, sendo 57,7/s a mais utilizada e filtro de 30-3000 Hz, com uma janela de 15 ms de duração. Para taxa do estímulo a maioria dos estudos utilizou de 2048, e um total de estímulos de 2 registros. O Potencial Evocado Auditivo de Tronco Encefálico é um exame que vem sendo pesquisado há muitos anos e muito se tem descrito na literatura sobre seus aspectos de aquisição e analise, além de destacar a importância da sua utilização na população neonatal.

Bone conduction: an explanation for this phenomenon comprising complex mechanisms

Bone conduction hearing inevitably involves vibration of the basilar membrane in response to a pressure gradient on either side of the membrane. The propagated wave that symbolizes this vibration of the basilar membrane can be triggered intentionally, when a bone vibrator is placed on the mastoid bone, or inadvertently when testing hearing of one ear by air conduction while disregarding transmission of the sound to the other side. When hearing is tested with a bone vibrator, the pathways leading to the basilar membrane can be divided into two main categories. The first type of pathway short-circuits the middle ear and comprises three distinct mechanisms: cochlear fluid inertia, compression of the cochlear walls, and pressure changes exerted via cerebrospinal fluid. In the second type of pathway, the stimulus reaches the basilar membrane via the middle ear, either directly or via the outer ear. Although it is difficult to precisely determine the contribution of each of these pathways to the basilar membrane, bone conduction remains the clinically most reliable way of directly testing cochlear function.

Acoustic events and "optophonic" cochlear responses induced by pulsed near-infrared laser

Optical stimulation of neural tissue within the cochlea was described as a possible alternative to electrical stimulation. Most optical stimulation was performed with pulsed lasers operating with near-infrared (NIR) light and in thermal confinement. Under these conditions, the coexistence of laser-induced optoacoustic stimulation of the cochlea ("optophony") has not been analyzed yet. This study demonstrates that pulsed 1850-nm laser light used for neural stimulation also results in sound pressure levels up to 62 dB peak-to-peak equivalent sound pressure level (SPL) in air. The sound field was confined to a small volume along the laser beam. In dry nitrogen, laser-induced acoustic events disappeared. Hydrophone measurements demonstrated pressure waves for laser fibers immersed in water. In hearing rats, laser-evoked signals were recorded from the cochlea without targeting neural tissue. The signals showed a two-domain response differing in amplitude and latency functions, as well as sensitivity to white-noise masking. The first component had characteristics of a cochlear microphonic potential, and the second component was characteristic for a compound action potential. The present data demonstrate that laser-evoked acoustic events can stimulate a hearing cochlea. Whenever optical stimulation is used, care must be taken to distinguish between such "optophony" and the true optoneural response.

Auditory brainstem and cortical potentials following bone-anchored hearing aid stimulation

Patients suffering from conductive or mixed hearing loss and Single-Sided Deafness may benefit from implantable hearing devices relying on bone conducted auditory stimulation. However, with only passively cooperative patients, objective methods are needed to estimate the aided and unaided pure-tone audiogram. This study focuses on the feasibility aspect of an electrophysiological determination of the hearing thresholds with bone-anchored hearing aid stimulation. Therefore, 10 normal-hearing subjects were provided with a Baha Intenso (Cochlear Ltd.) which was temporarily connected to the Baha Softband (Cochlear Ltd.). Auditory evoked potentials were measured by auditory stimulation paradigm used in clinical routine. The amplitudes, latencies, and thresholds of the resulting auditory brainstem responses (ABR) and the cortically evoked responses (CAEP) were correlated with the respective responses without the use of the Baha Intenso. The recording of ABR and CAEP by delivering the stimuli to the Baha results in response waveforms which are comparable to those evoked by earphone stimulation and appears appropriate to be measured using the Baha Intenso as stimulator. At the ABR recordings a stimulus artifact at higher stimulation levels and a constant latency shift caused by the Baha Intenso has to be considered. The CAEP recording appeared promising as a frequency specific objective method to approve the fitting of bone-anchored hearing aids. At all measurements, the ABR and CAEP thresholds seem to be consistent with the normal hearing of the investigated participants. Thus, a recording of auditory evoked potentials using a Baha is in general possible if specific limitations are considered.

Normative Auditory Brainstem Response Data for Hearing Threshold in the Rabbit

In an experimental study, we determined the physiological hearing threshold of the rabbit in order to use these data as normative values for further experimental investigations. The aim was to use different acoustic stimuli (click and tone-pip stimuli) with different frequency spectra for air and bone conduction (BC) in order to obtain further information about the optimal form of stimulus when recording auditory evoked potentials in the rabbit. For the investigation, we used 46 female New Zealand rabbits weighing 3.2-4.4 kg and aged 6 months. The equipment used to record brainstem auditory evoked potentials was the Nicolet Viking IV P System (Nicolet Biomedical, Inc.). In accordance with the experimental set-up, the measurements took place under intubation anesthesia, with a total of four repeat measurements performed on each ear at different times. Tone-pip and click stimuli with varying intensities of stimulus, transmitted via air conduction and BC, were applied. The I-IV waves proved the most stable for both stimulus modalities. They were registrable in 98.7% of cases, whereas only 30.2% of the V waves could be recorded. Values averaged from all measurements made throughout the study yielded a potential threshold of 34.8 dB peak equivalent (p.e.) SPL for the click stimulus, 13.8 dB p.e. SPL for the tone-pip stimulus at 8 kHz and 34.2 dB p.e. SPL for the click stimulus transmitted via BC. With regard to latencies, the results indicated a good reproducibility through different stimuli with acceptable standard deviations. The values for physiological hearing threshold obtained here can serve as normative data in subsequent experimental animal studies.

[Bone conduction auditory brainstem responses in normal hearing individuals]

BACKGROUND

bone conduction auditory brainstem responses (ABR) in normal hearing individuals.

AIM

to evaluate the clinical applicability of bone conduction ABR, characterizing normality and determining an assessment protocol.

METHOD

participants of this study were 22 individuals with normal hearing (20dB NA), with ages between 20 and 30 years, 14 female and 8 male. All individuals were assessed using air and bone (vibrator positioned on the forehead and mastoid) conduction ABR. EP25 equipment, Interacoustic; 3A insertion phone; B-71 bone vibrator; click stimulus.

RESULTS

it was possible to evaluate the bone conduction ABR in all individuals. The results demonstrate that the electrophysiological threshold obtained when the vibrator was positioned on the forehead (32.69+/-5.63 and 32.5+/-7.07dB nHL) was higher than that obtained when the vibrator was positioned on the mastoid (25.00+/-7.33 and 30.00+/-5.34dB nHL) for both genders respectively. For this reason the vibrator was positioned on the mastoid. The electrophysiological threshold obtained by bone conduction was higher than that obtained by air conduction for both genders and also when all individuals were grouped together. Thus it is necessary to use a correction factor, according to the results, of 10dB nHL. The latency-intensity values of the V wave in the ipsilateral and contralateral recordings differed statistically according to gender, and should be considered separately. The value of 26.81+/-6.99dB nHL was adopted as being the normal threshold for bone conduction ABR.

CONCLUSION

it is possible to evaluate bone conduction ABR in the clinical environment. These results, when considered along with the air conduction ABR, increase the chances of a more precise diagnosis regarding the type of hearing loss.

Bone-Conducted Sound: Physiological and Clinical Aspects

OBJECTIVE

The fact that vibration of the skull causes a hearing sensation has been known since the 19th century. This mode of hearing was termed hearing by bone conduction. Although there has been more than a century of research on hearing by bone conduction, its physiology is not completely understood. Lately, new insights into the physiology of hearing by bone conduction have been reported. Knowledge of the physiology, clinical aspects, and limitations of bone conduction sound is important for clinicians dealing with hearing loss and is the purpose of this review.

DATA SOURCES

The data were compiled from the published literature in the areas of clinical bone conduction hearing, bone conduction hearing aids, basic research on bone conduction physiology, and recent research on bone conduction hearing from our laboratory.

CONCLUSION

Five factors contributing to bone conduction hearing have been identified: 1) sound radiated into the external ear canal, 2) middle ear ossicle inertia, 3) inertia of the cochlear fluids, 4) compression of the cochlear walls, and 5) pressure transmission from the cerebrospinal fluid. Of these five, inertia of the cochlear fluid seems most important. Bone conduction sound is believed to reflect the true cochlear function; however, certain conditions such as middle ear diseases can affect bone conduction sensitivity, but less than for air conduction. The bone conduction route can also be used for hearing aids; since the bone conduction route is less efficient than the air conduction route, bone conduction hearing aids are primarily used for hearing losses where air conduction hearing aids are contraindicated.

Air versus bone conduction: an equal loudness investigation

Air conduction (AC) versus bone conduction (BC) loudness balance testing was conducted at frequencies of 0.25, 0.5, 0.75, 1, 2, and 4 kHz for two groups: 23 normal hearing subjects and eight subjects with a mild to moderate pure sensorineural hearing loss. Narrow-band noise was presented interchangeably between earphones and a bone transducer fitted to the subjects. Loudness matching was carried out at each frequency and at the levels 30-80 dB hearing level (HL) (10 dB steps) in the following manner: the sound pressure from the earphones was fixed and the subject adjusted the output level of the bone transducer for equal loudness by bracketing the standard. The results revealed somewhat different loudness functions for AC and BC sound with a 6-10 dB difference in the AC and BC loudness functions for the normal hearing group over the dynamic range 30-80 dB HL at the frequencies 250-750 Hz. At the higher frequencies, 1-4 kHz, the difference was only 4-5 dB over the same dynamic range. Similar results were obtained for the sensorineural hearing-impaired group. The difference between the AC and the BC loudness functions may originate from changes with level of the AC sound path, e.g. contraction of the stapedius muscle, but also distortion from the bone transducer and tactile stimulation could have contributed to the results seen.

The latency of auditory nerve brainstem evoked responses to air- and bone-conducted stimuli

The auditory nerve brainstem evoked responses (ABRs) to bone conduction (BC) stimuli are longer in latency than those to air conduction (AC). In order to study the mechanism of this difference, ABR wave I was recorded in experimental animals in response to low intensity (0-20 dB above their threshold) logon stimuli delivered by BC and by using the same bone vibrator to generate the air-conducted stimulus. The BC stimuli were delivered to skull bone, and directly to the contents of the cranial cavity (brain and cerebrospinal fluid) through a craniotomy. ABR wave I in response to BC stimuli delivered to skull bone was significantly longer in latency than that to BC delivered on the brain, while there was no latency difference between AC stimuli and BC to the brain. Furthermore, the vibration (measured with an accelerometer) recorded on the brain during BC stimulation of skull bone was always delayed compared to that measured on the skull. Thus there is a delay in the transfer of vibratory energy from the skull bone to the underlying contents of the cranial cavity. From there, the delayed vibrations of the contents of the cranial cavity are transmitted to the inner ear. This is probably the mechanism of the longer latency BC response compared to the AC response.

Frequency-specific brainstem responses to bone-conducted tone pulses masked by notched noise

As in the case of auditory brainstem responses (ABRs) to air-conducted stimuli, recording of frequency-specific ABRs to bone-conducted stimuli needs adequate masking of those parts of the basilar membrane that are not to contribute to the ABR. The present study shows that tone-pulse stimulation with notched noise-masking can be realized via a bone vibrator after its frequency response has been flattened. The latency-intensity curves for 4, 2, 1, and 0.5 kHz run approximately parallel, indicating the ABR to be indeed frequency-specific. As adequate air-conducted masking of the nontest ear can produce cross-masking, the use of an insert earphone is proposed. Because of its higher interaural attenuation, a higher masking level can be applied to the nontest ear.

Auditory brainstem response to bone-conducted clicks in adults and infants with normal hearing and conductive hearing loss

Knowledge concerning auditory brainstem response (ABR) by bone conduction (BC) is limited, and occasionally controversial. The present study was aimed at further elaboration of this issue. The research population consisted of 107 subjects. Four groups were investigated: group 1, normal-hearing adults aged 20-37 years; group 2, 10 children aged 5.6-8.4 years, with confirmed middle ear effusion (MEE); groups 3 and 4, 22 infants, matched by pairs, aged 5-18 months, 11 with normal otoscopy and 11 with suspected MEE. Comparison between ABR by AC and BC for all four groups is discussed. We observed that the AC-ABR threshold of group 2 was statistically significantly elevated compared to group 1. The same tendency was observed for group 4 compared to group 3. In AC ABR, the mean latency of wave V was significantly prolonged, compared to that of BC ABR in children with confirmed MEE, and infants with suspected MEE. We strongly suggest that by combining AC and BC ABR, more information concerning cochlear reserve status can be obtained in infants and young children who are difficult to test, or wherever a behavioral audiogram cannot be achieved.

Hearing loss in infants with craniofacial anomalies

Results of auditory brainstem response (ABR) evaluation of 145 infants, ages 6 months and younger with craniofacial anomalies (CFA), were examined to determined predicted degree and nature of hearing loss. Approximately 50% of infants demonstrated at least mild bilateral hearing loss. Presence and degree of hearing loss varied by CFA. All infants with bilateral aural atresia exhibited at least a moderate bilateral hearing loss; less than 20% of infants with isolated external ear anomalies (ear tags, isolated microtia) exhibited any degree of hearing loss. In 92% of infants with hearing loss, results of ABR were consistent with primarily conductive dysfunction. Implications for early identification and audiologic management of infants with CFA and hearing loss are discussed.

Relative effective frequency response of bone versus air conduction stimulation examined via masking

An adaptation of the sensorineural acuity level procedure was employed to obtain thresholds under bone- (BC) vs. air-conducted (AC) white noise masking. For the BC masking condition, a Radioear B71 was placed on one mastoid. An Etymotic ER3 with a foam tip placed in the ear on the same side was used to deliver the pure-tone probe stimulus. This transducer was chosen to approximate the Telephonics TDH-39 earphone response characteristic while reducing occlusion effect. For the AC masking condition, the masker and probe were mixed electrically and delivered to the earphone. Masked threshold data, transformed into frequency response curves, demonstrated greater variance of BC vs. AC response across frequency but less high-frequency roll-off than expected from coupler measurements obtained using an artificial mastoid and 6-cm3 cavity, respectively.

The masked threshold to noise ratio in brainstem electric response audiometry: assessment of the conductive loss component by bone-conducted masking

The aim of this study was to assess the conductive loss component (CLC) by brainstem electric response audiometry. A bone-conducted noise was used to mask out the response to a conventional air-conducted click stimulus. The difference between the levels of the click and the noise is defined as the masked threshold to noise ratio (MTNR). This MTNR was determined for 21 normal ears (MTNR = -13 +/- 5 dB). The increase in MTNR compared to this normative value is a measure of the CLC. For 10 ears with an artificially induced purely conductive loss, the increase in MTNR is in good agreement with the results of conventional pure-tone and brainstem electric response audiometry.

Normal infant and adult auditory brainstem responses to bone-conducted tones

Auditory brainstem responses (ABRs) were recorded to 500- and 2000-Hz bone-conducted (BC) tones from normal infants and adults. Infant ABR thresholds for the 500-Hz BC tones are significantly lower than their thresholds to 2000-Hz BC tones. Infant wave V latencies to 500-Hz BC tones are significantly shorter than those of adults, whereas infant and adult responses to 2000-Hz BC tones are similar in latency, suggesting that the effective intensity of the BC tones may be 9-17 dB greater for infants than for adults. A marked asymmetry between the ipsilaterally and contralaterally recorded wave V is seen for infant responses to 500- and 2000-Hz tones at all intensities; this asymmetry is not as evident in adults, except near threshold.

Frequency-specific auditory brainstem responses to bone-conducted stimuli

The feasibility of recording bone-conducted auditory brainstem responses (ABRs) to 500-Hz and 2000-Hz tone bursts and clicks was investigated in normal-hearing adults. For all 3 stimuli, responses were detectable in all subjects at 30 dB nHL. At 20 dB nHL, the tone burst responses were detectable in 80-87% of the subjects, demonstrating that even the responses to 500-Hz tone bursts were relatively robust. Latencies and amplitudes of the responses were related to the stimuli. The cochlear locations contributing to the responses were investigated using high-pass masking. Derived-band analysis indicated reasonably good frequency specificity for the tone burst responses and a broad representation for the bone-conducted click, despite its lower frequency spectrum. The results of this study support the use of bone-conducted tone burst ABR for demonstrating frequency-specific normal cochlear sensitivity.

Auditory brain stem responses to bone-conducted tones in infants

The auditory brain stem responses (ABRs) to 500- and 2,000-Hz bone-conducted (BC) tones were recorded from 48 infants with ears exhibiting various external and middle ear states (normal, otitis media, auditory meatal atresia). Amplitudes were greater, wave V latencies longer, and detectability better for responses to 500-Hz BC tones compared to 2,000-Hz BC tones. Overall, most (94% to 100%) infants with normal cochlear sensitivity demonstrate ABRs to 20-dB normal hearing level (nHL) 500-Hz BC tones and 30-dB nHL 2,000-Hz BC tones. In cases in which masking is difficult (eg, bilateral atresia), infant ipsilateral/contralateral ABR asymmetries may help determine from which cochlea a response to the BC tones originates. In conclusion, two-channel ABR recordings to BC tones appear to be feasible for demonstrating normal cochlear sensitivity in infants.

The psychological, educational and auditory sequelae of early, persistent secretory otitis media

Previous studies have suggested an association between chronic middle ear disorders due to secretory otitis media and adverse effects on auditory, educational and psychological development in children. Experimental design of such studies has often been poor. In this study, attempts were made to control extraneous variables more rigorously, using matched pairs. A group of children (n = 10) without current hearing problems but with a history of recurrent early secretory otitis media, aged 7-11 yrs, were compared on auditory, educational and psychological measures with a matched group of children with no history of otitis media. The results indicated weak but distinct differences between the two groups on the educational and psychological measures in favour of the control group. The implications for medical and educational services are outlined.

Validity of bone conduction stimulated ABR, MLR and otoacoustic emissions

The present study considers the validity of objective auditory investigation via bone conduction. Auditory Brainstem Responses (ABR) and Middle Latency Responses (MLR) were recorded in response to a bone vibrator stimulation with or without continuous bilateral air white noise masking. In all cases, such masking was found to result in an absence of recorded evoked potentials. It shows that under bone-conducted stimulation the evoked potential recorded is purely auditory, with no additional mechanical somatosensory component. In a further study, the feasibility of oto-acoustic emissions (OAEs) via bone conduction is demonstrated. These OAEs are, for a given subject, comparable to those found for air-transmission stimulation.

Click ABR intensity-latency characteristics in diagnosing conductive and cochlear hearing losses

A schematic description of the correlation between various pathologies of hearing impairments and the behavior of auditory brainstem responses (ABR) is presented. Conductive pathology and high-frequency cochlear hearing losses prolong wave component latency due to energy loss and hair cell dysfunction. In cases of flat cochlear hearing loss latency is not affected. Prolonged interwave latencies between wave I and wave V indicate eight nerve and brainstem disorders. An algorithm was developed in the form of a flow chart for locating various malfunctions. Fields of wave V intensity-latency functions were designed for the faster detection and more precise evaluation of conductive and cochlear hearing losses.

Brainstem response audiometry. II. Classification of hearing loss by discriminant analysis

In the companion paper [V.d. Drift et al.; Audiology 27: 260-270, 1988], it was shown graphically that conductive and cochlear hearing loss can be distinguished on the basis of the combinations of the auditory brainstem response threshold with the horizontal shift of the latency-level curve of peak V, its derivative or the latency of peak V at threshold level, respectively. In addition to the patient data used in the companion paper, 22 patients with mixed hearing loss were enrolled in the present study. The statistical technique of discriminant analysis was applied to find the optimum linear combination of auditory brainstem response data for classification of a hearing loss. The brainstem classification 'cochlear hearing loss' agrees with the diagnosis on the basis of the pure-tone audiogram in 85% of the cases. In cases with the brainstem classification 'conductive hearing loss', 93% showed at least a conductive component in the pure-tone audiogram.

Bone conduction masking for brainstem auditory-evoked potentials (BAEP) in pediatric audiological evaluations. Validation of the test

A brainstem auditory-evoked potential (BAEP) protocol for testing pediatric patients at risk for conductive hearing impairment was evaluated. The protocol used was: air-conducted click stimuli masked by bone-conducted wide-band noise. The specificity and sensitivity values for the test were determined by means of a blind cross-sectional trial including an active group of patients with an aural malformation and an age-matched control group with a sensorineural impairment. The bone-conducted masking of air-conducted BAEP showed high specificity and sensitivity and was easily administered despite pediatric difficulty. It was useful in differentiating sensorineural from conductive impairment and provided a rough estimate of the cochlear reserve in presumptive conductive hearing loss as great as 60 dB hearing loss. It is concluded that the bone-conducted masking procedure appears to be a great help in the binary decision whether middle ear surgery should be performed in patients at risk for conductive hearing loss, specially children with aural malformations.

Air and bone conduction brain stem responses in adults and infants

Air and bone conduction brain stem responses were recorded in 20 adults and 20 infants (16-20 months postconceptional age) with normal hearing. The stimuli were administered using a shielded TDH-39 headphone and a standard B-70A vibrator. Our results show that adults and infants have similar air and bone conduction brain stem thresholds. The comparison of input latency functions obtained with air and bone conduction clicks indicates that the acoustic stimulus generated by the bone vibrator excites more apical regions than that stimulated by the air conduction transient. This is related to the spectrum of the bone conduction click which has an energy peak at 1-2 kHz. Furthermore we found that the difference in latency between adults and infants for air-conducted clicks decreases along with the stimulus intensity and the latencies tend to overlap near the threshold.

Comparison of the latencies between bone and air conduction in the auditory brain stem evoked potential

Brain stem auditory evoked potentials obtained by air and bone conduction were investigated in 22 subjects. The necessity for a carefully selected stimulus being presented to the headphone and the bone vibrator is discussed. Latency values of both responses are presented for wave V. Bone conduction showed latencies which were longer than those obtained by air conduction (about 0.9 msec). Possible mechanisms for this delay are discussed.