博士 / 國立臺灣大學 / 醫學工程學研究所 / 96 / Background/Purpose: Objective measurement by tone burst evoked auditory brainstem response provides relatively accurate estimates of the behavioral auditory thresholds at speech frequencies. The first part of this study reports the preliminary data of tone burst auditory brainstem response measurements in infants and very young children. As an excellent agreement and correlation between objective evoked-potential and subjective behavioral thresholds have been demonstrated by previous studies, the second part of this study investigates the effects of different age and degree of hearing loss on the above agreement and correlation. Comparison was made between objective tone burst auditory brainstem responses and subjective sound field audiometry. To further compare the differences between objective and subjective measures, the third part of this study applied another evoked potentials test to investigate if the subjective tinnitus demonstrates increased intensity dependence objectively at the selected frequencies.
Methods: Of the part one study, 94 infants and very young children from 3 months to 3 years of age underwent tone burst auditory brainstem response measurements at selected four frequencies. Statistical methods were applied to study the relationship among recorded variables. In the part two, 1281 infants and very young children aged from 3 months to 3 years underwent diagnostic audiometry including sound field audiometry and tone burst auditory brainstem response measurements. Statistical analyses were applied to investigate the effects of age and hearing loss on the agreement and correlation between two measured thresholds. In the part three, we applied auditory cortical evoked potential test to investigate 9 tinnitus patients and 9 age- and sex-matched healthy subjects without tinnitus. Auditory cortical evoked potentials (N1-P2) were elicited from stimuli at four frequencies (4000, 2000, 1000 and 500 Hz) with five intensities (50, 56, 62, 68 and 74 dB nHL). Intensity dependences by latency of N1 and amplitude of N1-P2 were surveyed at midline electrodes.
Results: The results of part one indicate that the averaged tone burst auditory brainstem response thresholds of the infants and young children with normal hearing in Taiwan are typically 10 to 20 dB nHL at 500, 1000, 2000, and 4000 Hz. There is no statistically difference for the thresholds regarding gender, laterality, and age distribution in this study. In part two, significant correlations (Ps＜0.001) were seen between two measured thresholds across groups of different ages and different degree of hearing loss more than 20 dB HL. However, the correlation strength deteriorated along with decreased degree of hearing loss. Correlations for hearing thresholds less than 20 dB HL were not significant at 1000, 2000 and 4000 Hz. In part three, significant differences existed in the intensity dependence of amplitude N1-P2 to the pooled frequencies at Fz and Cz position. These differences suggested that tinnitus patients tended to respond less to increased sound intensity and were inclined to weaker intensity dependence.
Conclusion: Based on the published research and our study, we suggest setting the normal criterion levels for the infants and young children in Taiwan of the tone burst auditory brainstem response to air-conducted tones as 30 dB nHL for 500 and 1000 Hz, and 25 dB nHL for 2000 and 4000 Hz. From part two, properly obtained and interpreted with respect to the effects of age and degree of hearing loss, the evoked potentials test provide the very informative hearing threshold reference to perfect the behavioral audiometric evaluation for the infants and very young children with hearing loss. From part three, objectively increased intensity dependence of N1-P2 component at selected frequency can not be demonstrated in tinnitus patients with normal hearing. Restated, the edge frequency phenomenon fails to present in tinnitus patients with normal hearing, a different characteristic from tinnitus patients with hearing loss.
| Identifer | oai:union.ndltd.org:TW/096NTU05530010 |
| Date | January 2008 |
| Creators | Chung-Yi Lee, 李仲毅 |
| Contributors | 趙福杉 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 95 |
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