객관적으로 청력역치를 측정하는데 청성뇌간반응(auditory brainstem response, ABR)은 가장 효과적인 유발전위(evoked potential) 검사로 폭넓게 인식되어 왔다. 임상적으로 주로 사용되는 클릭음은 1,000~4,000 Hz의 순음평균역치와 높은 상관관계를 나타내어 1,000 Hz이하의 저주파수의 정보를 얻을 수 없는 단점이 있다. 반면 저주파수 청력을 평가할 수 있는 Toneburst자극을 사용하는 청성 뇌간반응은 주파수 특이성을 가지며 순음청력역치의 500~4,000 Hz를 평가할 수 있으나 파형이 명확치 않아 파형의 해석에서 차이를 보인다. 더욱이 청성뇌간반응의 최대자극 강도는 90 dBnHL로 고심도 난청환자의 역치를 측정하는
Currently, the auditory brainstem responses (ABRs) are widely recognized as the most effective evoked potential test. However, ABRs are limited by restrictions on maximum presentation levels (90 dBnHL) and by subjective interpretational process for determining threshold. To compensate those limitations auditory steady- state responses (ASSR) is recently developed. The goal of this study was to compare the degree between ASSR thresholds and pure tone thresholds in the sensorineural hearing impaired. Multiple auditory steady- state responses were evoked by eight tonal stimuli (four per ear), with each stimulus simultaneously modulated in both amplitude and frequency. The modulation frequencies varied from 66 to 99 Hz and the carrier frequencies were 500, 1000, 2000 and 4000 Hz. 40 normal ears and 65 sensorineural hearing impaired ears participated. The differences between ASSR thresholds and pure tone thresholds in the sensorineural hearing impaired and the normal hearing were 15.0±8.3, 12.4±8.5, 12.4± 8.0 and 16.2±9.1 for 500, 1,000, 2,000 and 4,000 Hz carrier frequencies, respectively. The correlation coefficients were 0.966, 0.969, 0.972 and 0.958 for each frequency. The differences between ASSR thresholds and pure tone thresholds in the sensorineural hearing impaired were 7.6± 13.3, 0.2±12.3, 1.0±12.9, 1.2±16.3 for 500, 1,000, 2,000 and 4,000 Hz carrier frequencies, respectively. The differences between ASSR thresholds and pure tone thresholds in the normal ears were 18.5±7.2, 17.0±8.0, 15.8±7.6, 20.3±8.2 for 500, 1,000, 2,000 and 4,000 Hz carrier frequencies, respectively. The correlation coefficients were 0.160, 0.105, 0.224 and 0.202 for each frequency. Further, the sensorineural hearing impaired group was divided into two groups, pure tone average (PTA) lower than 100 dB and PTA higher than 100 dB. The differences between ASSR thresholds and pure tone thresholds in the sensorineural hearing impaired higher than PTA 100 dB were -1.3±13.2, -9.1±10.4, -9.2±10.6, -12.7±11.6 for 500, 1,000, 2,000 and 4,000 Hz carrier frequencies, respectively. The differences between ASSR thresholds and pure tone thresholds in the sensorineural hearing impaired lower than PTA 100 dB were 14.3±8.9, 7.3±8.4, 8.8±8.2, 11.6±10.6 for 500, 1,000, 2,000 and 4,000 Hz carrier frequencies, respectively. These results indicate that ASSR testing to be extremely helpful in the evaluation with the sensorineural hearing impaired especially with the sensorineural hearing impaired higher than 100 dB. The ASSR method provides good estimates of the degree of hearing in individuals with the sensorineural hearing impaired. KEY WORDS：Auditory steady-state response (ASSR)·SNHL
INTRODUCTION MATERALS AND METHODS RESULTS DISSCUSSIONS CONCLUSIONS REFERENCES
