Evaluation of noise-induced hearing loss by auditory steady-state and auditory brainstem-evoked responses

Noise-induced hearing loss (NIHL) may result from occupational noise exposures and is considered as an 'Occupational Disease'; therefore, it is compensable. To verify the existence and severity of the work-related hearing loss, there is a need of an objective, reliable auditory measure in cases of arbitration of financial disputes to resolve any medicolegal aspects. The objective of the study was to compare between the ABR and ASSR for predicting the behavioural threshold in subjects with normal hearing or NIHL.

The study included 82 subjects regularly exposed to high levels of occupational noise, with normal hearing and NIHL. ABR to clicks and to tone bursts were recorded followed by multiple-frequency ASSR. Physiological and behavioural thresholds were compared for specific frequencies (1000, 2000 Hz) and average of high-frequency range (2000 and 4000 Hz). In addition, Pearson correlations and the specificity and sensitivity of each measure were also calculated using receiver operating characteristic (ROC) curves.

In the NIHL group, there was a significantly smaller difference between the behavioural threshold and click-ABR than the ASSR in high-frequency range. Pearson correlations were significantly higher for click-ABR. Analysis of specific frequencies yielded a smaller difference between behavioural and ASSR than tone-burst-ABR thresholds, with a slightly better correlation for ASSR than tone-burst-ABR. Higher sensitivity but lower specificity was suggested for ASSR than ABR.

ASSR is associated with high-frequency specificity, shorter test sessions and good correlations with behavioural thresholds, making it a potentially better measure than ABR for predicting audiograms in subjects with NIHL. These findings have diagnostic implications, especially in cases of workers' compensation when subjects may be uncooperative.