Auditory brainstem and middle latency responses to 1 kHz tones in noise-masked normally-hearing and sensorineurally hearing-impaired adults

Abstract

The present study provides comparative evaluation of the ABR and MLR to 1 kHz brief tones in two groups of hearing-impaired subjects (noise-masked normally-hearing; and sensorineurally hearing-impaired adults), as well as a normally-hearing control group. Tones were presented at intensities from threshold to 80–90 dB nHL. The results of this study show that: (1) the ABR and MLR to these low-frequency (1 kHz) tones are equally accurate in estimating hearing threshold, (2) at supra-threshold levels, there are differences in the ABRs and MLRs for subjects with decreased hearing sensitivity resulting from cochlear pathology, compared to those obtained from adults with simulated hearing loss due to broadband masking, and (3) supra-threshold stimuli produce differential effects on the latency and amplitude characteristics of the ABR and MLR in listeners with true sensorineural hearing impairments. Possible physiologic explanations are offered for this differential pattern of results.

• ABR/MLR
• Threshold estimation
• Supra threshold
• Hearing-impaired
• Masking

Sumario

El presente estudio permite una evaluación comparativa de las ABR y las MLR con tonos breves de 1 kHz en dos grupos de sujetos con impedimentos auditivos (normoyentes con enmascaramiento por ruido y adultos con hipoacusias sensorineurales) así como en un grupo control de normoyentes. Se presentaron los tonos a intensidades que fueron desde el nivel de umbral hasta 80–90 dB nHL. Los resultados de este estudio muestran que:(1) Las ABR y MLR a estos tonos de baja frecuencia (1 kHz) son igualmente precisas para estimar los umbrales auditivos. (2) en niveles supraliminares hay diferencias en las ABRs y las MLRs en sujetos con sensibilidad auditiva disminuida que resulta de patología coclear, comparada con las respuestas obtenidas en adultos con pérdida auditiva simulada por enmascaramiento de banda ancha y (3) los estímulos supraliminares producen efectos diferenciales en las características de latencia y amplitud de las ABR y las MLR en sujetos con verdaderos impedimentos sensorineurales. Se ofrecen posibles explicaciones fisiológicas para este patrón diferencial de resultados.

Notes

Judges viewed the whole ABR/MLR waveform. It is possible, therefore, that the presence/absence of one peak could influence the decision about the other peak. Judges were instructed to use specific latency windows when judging a peak, and the results show that sometimes the ABR threshold was lower, while other times the MLR threshold was lower. Beyond this, however, observer bias could not be controlled.