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目的初步探讨犬术中大脑皮质中央沟定位(central sulcus localization,CSL)及运动诱发电位(motor evoked potential,MEP)的方法。方法选取健康比格犬5只,皮下针状电极刺激前肢正中神经,记录大脑皮质的躯体感觉诱发电位(somatosensary evoked potentials,SSEP),从而定位中央沟。皮质电极置于左右大脑半球皮质,皮下针状电极置于左侧拇短展肌(left abductor pollicis brevis,LAPB),分别采用单相阳极、单相阴极及双极恒流刺激,记录LAPB的MEP波形并比较潜伏期。采用单相阳极恒压刺激,观察不同刺激脉冲数(5、7个/串)、脉宽(0.075、0.050 ms)及刺激频率(150、250、350 Hz)下MEP潜伏期变化。结果 SSEP在大脑皮质发生相位翻转,第1个正相主波和负相主波的平均潜伏期分别为(15.4±2.1)、(16.3±2.0)ms,二者之间无统计学差异(P>0.05)。单相阳极、单相阴极及双极刺激诱发MEP的平均潜伏期分别为(31.7±1.8)、(29.0±3.9)、(40.0±1.6)ms,阈刺激强度分别为5.0、5.5、6.0 m A。刺激脉冲数为7个/串时MEP平均潜伏期小于5个/串(P<0.05),脉宽为0.075 ms时MEP平均潜伏期小于0.050 ms(P<0.05),刺激频率为350 Hz时MEP平均潜伏期小于频率150 Hz(P<0.05)。结论刺激犬正中神经成功诱发SSEP,可区分中央沟两侧感觉区和运动区。刺激脉冲、脉宽、刺激频率均可影响MEP潜伏期。
Objective To investigate the method of central sulcus localization (CSL) and motor evoked potential (MEP) in canine cortex. Methods Five healthy Beagle dogs were selected and the subcutaneous needle electrodes were used to stimulate the median nerve of the forelimb. The somatosensory evoked potentials (SSEPs) of the cerebral cortex were recorded to locate the central sulcus. The cortical electrodes were placed on the left and right cerebral cortex, and the hypodermic needle electrodes were placed on the left abductor pollicis brevis (LAPB). Monophasic anodes, single-phase cathodes and bipolar constant-current stimulation were used to record the MEP Waveform and compare latency. The changes of MEP latency were observed under the condition of single-phase anodic constant voltage stimulation (5,7 cells per pulse), pulse width (0.075,0.050 ms) and stimulation frequency (150,250,350 Hz). Results The phase inversion of SSEP occurred in the cerebral cortex. The average latency of the first positive phase and negative phase was (15.4 ± 2.1) and (16.3 ± 2.0) ms, respectively. There was no significant difference between them (P> 0.05). The average latency of MEP induced by single-phase anode, single-phase cathode and bipolar stimulation were (31.7 ± 1.8), (29.0 ± 3.9) and (40.0 ± 1.6) ms, respectively. The threshold stimuli were 5.0, 5.5 and 6.0 mA, respectively. The average incubation period of MEP was less than 5 per bunch (P <0.05) when the number of stimulation pulses was 7 per bunch, and the average latency of MEP was less than 0.050 ms (P <0.05) when the width of pulse was 0.075 ms. Less than 150 Hz (P <0.05). Conclusion Stimulation of the canine median nerve successfully induces SSEP, which can distinguish the sensory zone and motor zone on both sides of the central canal. Stimulation pulse, pulse width, stimulation frequency can affect MEP latency.