Electrophysiologic threshold study in air and bone conduction in children with 2 months or less age

The differential diagnosis of hearing loss with air and bone Auditory Brainstem Response in small children has not been enough studied in Brazil.

AIM

To compare air and bone Auditory Brainstem Response results in children under 2 months of age with normal hearing.

STUDY DESIGN

clinical with transversal cohort.

MATERIALS AND METHODS

12 children who passed the hearing screening were evaluated using air and bone Auditory Brainstem Response. No contralateral masking was used in the bone conduction test. The responses were compared and analyzed by the McNemar test and repetitive measurements of the variance test.

RESULTS

There were no statistic differences between air and bone conduction Auditory Brainstem Response thresholds (p>0.05). The bone conduction latency for wave V was statistically higher than air conduction latency (p=0.000).

CONCLUSION

There was agreement on the results recorded for air and bone conduction Auditory Brainstem Response for threshold intensities; latency for bone conduction wave V was statistically higher than the air conduction latency.

Estudo dos limiares eletrofisiológicos das vias aérea e óssea em crianças com até 2 meses de idade

O diagnóstico diferencial de perdas auditivas com potencial evocado auditivo de tronco encefálico por via aérea e por via óssea em crianças pequenas tem sido pouco estudado no Brasil. OBJETIVO: Comparar as respostas do potencial evocado auditivo de tronco encefálico por vias aérea e óssea em crianças de até 2 meses de idade sem perdas auditivas. FORMA DE ESTUDO: Clínico prospectivo com coorte transversal. MATERIAL E MÉTODO: Foram avaliadas 12 crianças que passaram na triagem auditiva, por meio do potencial evocado auditivo de tronco encefálico por via aérea e via óssea. A via óssea foi realizada sem mascaramento contralateral. As respostas foram comparadas e analisadas por meio do teste de McNemar e pela análise de variância com medidas repetidas. RESULTADOS: Não houve diferença estatística no limiar eletrofisiológico por via aérea e via óssea (p>0,05). O tempo de latência por via óssea foi estatisticamente maior do que o tempo de latência por via aérea (p=0,000). CONCLUSÃO: Houve concordância no registro do Potencial Evocado Auditivo de Tronco Encefálico captado por vias aérea e óssea nas intensidades próximas ao limiar auditivo; a latência da onda V registrada por via óssea foi estatisticamente maior que a registrada por via aérea.

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.

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.

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

The variability of the auditory brainstem response (ABR) to bone- and air-conducted clicks was investigated utilizing a test-retest paradigm with 20 normal full-term newborn infants. ABRs to bone-conducted clicks at 15 and 30 dB nHL and air-conducted clicks at 30 dB nHL were obtained. The delivery of the bone-conducted signal was controlled. ABR wave V latencies were measured from each test-retest stimulus condition. The results indicated no statistically significant difference in test-retest variability of ABR wave V latencies or amplitudes between bone- and air-conducted clicks. ABRs to bone-conducted clicks, under controlled clinical conditions, are as reproducible and reliable as ABRs to air-conducted clicks in newborn infants.

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.

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.

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.