聴性誘発反応のmiddle latency responseの検討
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概要
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The properties of the auditory evoked response with peak latency of 6 to 50 cosec, whichwas often referred as "middle latency response", were studied in order to examine its clinical significance.The subjects used in this study were 8 adults, 5 young children aged from 2 years 2 months to 3 years 9 months and 4 infants aged from 12 months to 17 months.All the subjects were proved to have normal hearing.Active electrode was attached to the vertex while reference and ground electrodes were placed on one of the ear lobes and the root of the nose respectively.The responses were led to a medical computer through an amplifier and an analog filter set to pass bands of 1.8-2800 Hz in most cases, in order to minimize the effect of the filter on the recorded data.Two thousand signals were averaged in a test run and were recorded with an X-Y recorder.Clicks were used for auditory stimulation.The response pattern was relatively stable in adults and characterized by a polyphasic con-figulation with mean peak latencies of(Po) 6.4±0.31 msec, (Na) 16.7E 1.87 msec, (Pa) 28.4±3.82 msec, and(Nb) 40.3±2.84 msec with the stimulus intensity of 60 dBHL.Po-peak seemed to correspond to the so-called BSR.The mean peak to peak amplitudes were 1.35±0.14μV (Po-Na), 1.38±0.25, μV(Na-Pa), 1.34±0.12, μV(Pa-Nb), respectively(at 80 dBHL).In infants the response pattern was more variable and the peak latencies were shorter than those of adults except Po-peak.The mean peak to peak amplitudes in infants were smaller than those of adults and the values were different between the three parameters as in the following order;(Po-Na)(Na-Pa)>(Pa-Nb).Threshold for Pa-peak was 10 dBHL in adults, 25 dBHL in young children and 40 dBHL in infants.The response pattern was altered with cut-off frequencies of the filter bands.The stability, threshold and identification of the response were improved with narrow bands of 22.4-180 Hz especially in infants.In clinical use of this response, the effective bands should be selected.Although the frequency specificity of this response was not examined in the present study, it will be important problem in clinical application.
- 一般社団法人 日本耳鼻咽喉科学会の論文