고양이에서 와우갑각 및 정원창 전기자극 청성중간반응에 관한 연구
Promontory and round window stimulation electrical middle latency response in cat
와우갑각 정원창 전기자극 청성중간반응;
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목적 : 청성중간반응(middle latency response, MLR)은 주파수별 청력역치의 측정이 가능하고 고위청각기능을 평가하는데 장점이 있으며, 뇌간이후 중추신경계의 이상을 진단하는데 도움이 된다. 저자들은 고양이를 대상으로 와우갑각 전기자극 청성중간반응(Promontory stimulation electrical MLR, PS-EMLR) 및 정원창 전기자극 청성중간반응(round window stimulation electrical MLR, RW-EMLR)을 비교하여 임상적인 이용에 대한 기초자료를 마련하고자 본 연구를 실시하였다. 방법 : 고양이 8마리(1.5∼3.0Kg) 8귀를 대상으로 하였다. 이개반응 및 ABR로 정상청력임을 확인하였다. 마취상태(Ketamine+Xylazine, im)에서 와우갑각에 댄 전극을 통하여 전기자극을 주고 PS-EMLR을 측정한 후 같은 방법으로 RW-EMLR을 측정하였다. 전기자극은 monopolar, 250μ sec biphasic(12μ sec/phase, +/-) charge-balanced square wave pulse를 사용하였으며 자극빈도는 10회/sec로 하였다. 전두정중부에 활성전극과 자극 반대측 이개에 기준전극을 부착하였으며 유발전위의 기록은 Nicolet CA-2000 Evoked Response Audiometer를 이용하였다. 필터는 5∼1500Hz, 증폭기 sensitivity를 100μV, 기록시간을 100 msec 로 하여 256회 이상 평균가산 하였다. 결과 : PS-EMLR 및 RW-EMLR 모두에서 안정된 파형을 얻었다. 전형적인 파형은 5∼7개의 음성파 및 양성파로 구성되었으며 이중 PA가 가장 안정되고 뚜렷하게 관찰되었다. 평균역치는 각각 612±229.5μA, 362±140.8μA로 PS-EMLR이 통계적으로 유의하게 높았다.(P
Middle latency response (MLR) is a series of waveforms occurring from 8∼10 to 50∼80 msec after the onset of an auditory stimulus. It can be used in auditory sensitivity test especially in low frequency and also in assessing higher auditory pathway function. Promontory stimulation electrical middle latency response (PS-EMLR) is obtained relatively easily, but promontory is farther from spiral ganglion cells than round window, scala tympani and modiolus. Kileny, et al. reported that round window stimulation EMLR (RW-EMLR) maybe equally effective in activating the auditory pathways as scala tympani in guinia pig. Middle latency response were recorded in response to promontory and round window electrical stimulation in 8 cats in order to compare the two waves. Electrical stimuli at level ranging from 100μA monopolar, 250μsec biphasic (125μsec/phase, +/-), charge-balanced, square wave pulses presented at a rate of 10 pulse/sec were performed with an electrode placed on the promontory and round window respectively. A needle electrode was inserted in the periosteum overlying the bulla as a reference electrode. The EMLR was recorded by the active electrode placed on frontal pole zero(Fpz) and the reference electrode on the contralateral ear lobule. The following charateristics of the PS-EMLR and RW-EMLR were observed. 1) Typical PS-EMLR and RW-EMLR waveform in cat consisted of a series of five to seven positive and negative peaks and labelled waves N0, P0, NA, PA, NB, PB and NC according to latency. The PA was most obviously identified and stable. 2) The mean threshold of PS-EMLR was 612±229.5μA and that of RW-EMLR was 362±140.8μA. The mean threshold of PS-EMLR was greater than that observed for round window stimulation. 3) The mean latency of the wave PA in PS-EMLR at threshold was 20.82±2.59 ms and the mean latency of wave PA in RW-EMLR at threshold was 20.04±1.65 ms. There were no statistically significant changes in the latency of wave PA as the stimulus intensity increased. And there were no statistically significant differences between the two waves. 4) The amplitude of wave PA in PS-EMLR and RW-EMLR increased as the stimulus intensity increased. And there were no significant differences between the two waves including amplitude growth function. It is known that auditory neural survival is more corelated with amplitude growth function of the EMLR than threshold. As a result, PS-EMLR can be used more effectively in clinic to avoid a typanomeatal flap surgery because there is no significant difference in amplitude growth function of the two waves even though RW-EMLR has a lower threshold.