正常幼兒的骨導性腦幹聽性反應

Bone-Conducted Auditory Brainstem Response in Normal Young Children

以臨床應用為導向，報告骨導腦幹聽性反應檢查的刺激音校準和幼兒正常值設定的一例。測量對象為15名2歲聽力正常幼兒，兩耳對滴答聲的氣導腦幹聽性反應閾值均優於15 dB nHL(decibel normalized hearing level)，且行為觀察的聲場聽力檢查500、1000、2000和4000赫的聽閾均優於20分貝，骨導腦幹聽性反應檢查測試結果，刺激音強45、30和15 dB nHL的第V波平均潛時(msec)分別是6.63 ± 0.31、7.00 ± 0.36和7.63 ± 0.36，第V波平均波幅(μV)分別是0.34 ± 0.09，0.26 ± 0.07和0.17 ± 0.06。骨導性腦幹聽性反應的再現性良好，可應用於評估耳蝸的功能，幫助鑑別診斷傳音性聽力損失或感音神經性聽力損失。本報告的方法可推廣應用於新生兒或1歲以下嬰兒的骨導性腦幹聽性反應正常值的建立。

The auditory brainstem response (ABR) to bone-conducted clicks appears to be capable of providing information about the cochlear function. By using bone-conducted ABR, we can differentiate sensorineural hearing loss from conductive hearing loss in infants and young children. The purpose of this study is to establish clinical normal data for bone-conducted ABR in young Taiwanese children. We used a Nicolet Spirit (Wisconsin, USA) for ABR testing and recording. A bone vibrator (Radioear, Model B-70B, USA) was used to conduct clicks. The intensities of the bond-conducted clicks were calibrated relative to the average behavioral threshold of 10 adults with normal hearing who had been assessed by air-conducted pure tone audiometry to have hearing thresholds no worse than 10 dB HL at octave steps from 250 to 8000 Hz. The reference level (0 dB nHL) for the bone vibrator was 55.0 dB p( re: 1 dyne). The ABR to bone- conducted clicks were studied in 15 young children with normal hearing, aged from 1 year 11 months to 2 years 11 months. At first, they were assessed by air-conducted ABR and sound field audiometry to have hearing thresholds no worse than 15 dB nHL and 20 dB HL, respectively. During bone-conducted ABR testing, the bone vibrator was placed in a supero-posterior auricular position and fixed with an elastic band. The control and maintenance of the delivery of bone-conducted clicks are very important for evaluation of the absolute latencies and amplitudes of the ABR waves. The head coupling force to the bone vibrator should be controlled at 550-650 g. Various intensities (45 dB, 30 dB and 15 dB nHL) of bone-conducted clicks were used to evoke the ABR. Bone-conducted ABR to various intensities were recorded and stored for analysis.「he mean latencies(msec) of the wave V evoked by various stimulus intensities were as follows: 6.63 ± 0.31 for 45 dB nHL, 7.00 ± 0.36 for 30 dB nHL, and 7.63 ± 0.36 for 15 dB nHL. The mean amplitudes(μV) of the wave V evoked by various stimulus intensities were as follows: 0.34 ± 0.09 for 45 dB nHL, 0.26 ± 0.07 for 30 dB nHL, and 0.17 ± 0.06 for 15 dB nHL. In the near future, in order to diagnose sensorineural hearing loss earlier, the present method could be used to establish normal data for bone- conducted ABR for newborns and infants.