Changes of auditory brainstem response in the patients with noise-induced hearing loss

Objective To observe the changes of auditory brainstem response in the patients with noise-induced hearing loss. Methods Forty-seven workers exposed to occupational noises were tested by pure tone audiometry (PTA) and auditory brainstem response (ABR). All of the subjects were divided into 4 groups based on the patterns of PTA. The ABR results in each group were analysed and compared to their behavioral thresholds of PTA. Results (1)With the increase in the frequency and extent of hearing loss, the prolongation of wave Ⅴ latency at the lower stimulating level first occurred, followed by the prolongation or absence of wave Ⅰ, and then the abnormalities of wave Ⅲ toⅤat the higher level; In this process, wave Ⅴ thresholds gradually increased, which became more obvious in the latter stage of noise-induced hearing loss. (2)For the mild hearing loss at 4 kHz alone, the ABR abnormality mainly presented as prolonged wave Ⅴ latency at lower level and in half cases was the change of waveⅠat higher level. Conclusions (1)The ABR results of noise-induced hearing loss are correlated with a gradual pathological process from outer to inner hair cells, then to auditory nerve and brainstem auditory pathway. (2)For the suspected cases of noise-induced hearing loss, wave Ⅴ latency at lower level should be observed and combined with other auditory tests to make a logical diagnosis.