The Combining Use Of Response Threshold Of ABR Wave V And 40HzAERP To Assess People's Hearing Threshold

Objective and subjective hearing tests are two areas of hearing examination. Scientists have done a great deal of hard work on finding anefficiency way to evaluate human's hearing threshold. Auditory brainstem response has been used widely in clinical working. However, the thresholds of the wave V could just mirror the higher frequencies and also often be interfered by the diseases of the Vffl cranial nerve or of the brainstem. So using ABR individually to evaluate people's hearing thresholds could not get an accurate result. Using pure tone at 40/s as stimulus, recordings would write down a series of semi-sinusoidal waves with period of 25ms, which is called 40HzAERP. It is a specialty of MLRs, and has the advantages of frequency character > good repetitive and can be easily recognized for its larger amplitude. For 40HzAERP's limited documents on old people, our purpose is using ABR and 40HzAERP combined to exam both young and old people's hearing thresholds.Method: 44 persons were allowed to our experiment. Firstly, check their pure tone thresholds, that is their objective thresholds. Young people whose hearing curve bellowing 15 dB from 125 to SOOOFIz were permitted to next step. As for old persons, the standards were made by their ages. After impedance audiometry having been checked, subjects entered the third step: ABR and 40HzAERP on the condition of not being found any abnormal. Results: The thresholds of all frequencies for 40HzAERP inyoung adults are lower than those of the elders. However, though the difference has statistic significance, the numbers don't surpass 5 dB , so from clinical view, we say that there is no difference..In young group, the hearing curves of the objective test are flat; the difference between the wave V thresholds of the ABR and the behavior thresholds ( the average of 500. 1000, 2000Hz), the difference between the wave V thresholds and the pure tone's thresholds at 4000Hz, those two numbers don't do differstatistically. The difference between the wave V thresholds and the behavioral thresholds, the difference between the 40HzAERP and pure tone thresholds, these two numbers don't do differ clearly, too. So we conclude that ABR can mirror the subjects' hearing thresholds exactly in young adults.Documents have shown that the hearing curve of old people is marked with suddenly reducing at higher frequency . our testproved this theory. In our tests, old people's responsive points cut down suddenly at higher frequency and diffused obviously with frequency improving. The old person's responsive thresholds of 40HzAERP are higher than those of pure tone tests at all frequency (9.87 + 3.45, 8.37 + 4.31, 9.42 + 4.07 dB at 500, 1000, 2000 Hz separately). The thresholds of wave V is 8. 97 ?5.41 dB higher than that of pure tone tests at 4000Hz. The above four numbers are nearer and haven't any statistical difference; however, thethresholds of the wave V is 14.55?.85 dB higher than that of the behavioral thresholds. From the above, we can draw the conclusion that ABR's thresholds is nearer to behavior thresholds at lower frequencies than at higher fenquency. This phenomenon isn't-6-clear when the audiometric tone's curve is flat, foe example at young people; but it can't be missed when the audiometric curve cut down sharply at higher frequency,Conclusion: the thresholds of wave V of ABR can mirror just lower frequencies hearing thresholds; to appreciate one's hearing thresholds accurately, we should use ABR and 40HzAERP together at the same time, especially at people with suddenly cutting down audiometric curve.