Cozzi P, Poncelet L, Michaux C, Balligand M
Department of Small Animal Surgery, Faculty of Veterinary Medicine, University of Liege, Sart-Tilman, Belgium.
Am J Vet Res. 1998 Feb;59(2):217-20.
To investigate the effect of stimulus intensity on the characteristics of the spine recorded somatosensory evoked potentials (SEP) in dogs.
11 healthy Beagles, 1 to 2 years old.
In 10 dogs, square-wave stimuli (0.1-ms duration, 4 Hz) were delivered through needle electrodes inserted close to the right tibial nerve at the tibiotarsal joint. A standard stimulus strength (reference effective stimulus [RS]) was established for each dog by determining the stimulus necessary to induce a maximal M wave (muscle evoked potential) in the plantar interosseus muscles. The polarity of the stimulating electrodes was then reversed, and an SEP was recorded at the level of the T13-L1 interarcuate ligament. Subsequently, stimuli at fractions (1/4x, 1/2x) and multiples (2x, 4x) of RS were delivered. Recordings, using 10x RS stimuli, also were obtained in 2 dogs; in 1 of them, the recordings were obtained before and after curarization. In each instance, the latencies and the amplitudes of the first 3 reproducible deflections were measured and evaluated.
The SEP waveform recorded at the T13-L1 level using RS was similar in all dogs; at least 3 deflections were recognized. Altering stimulus intensity did not significantly change latency of the first 3 peaks; conversely, amplitudes of the first 3 peaks increased (P < 0.01) when the stimulus intensity was increased from 1/4x RS to 1x RS. Stimulation at 10x RS induced the recording of a large potential, which was suppressed by the curarization.
Only slight variations affect latency data through a wide range of stimulus intensities; latency measurement can be considered a robust tool in the vicinity of RS. Slight variations in the electrode position during an SEP session should not invalidate the results. Differences in the definition of the stimulus intensity among laboratories should not preclude the comparison of the results.
研究刺激强度对犬脊柱体感诱发电位（SEP）特征的影响。
11只1至2岁的健康比格犬。
对10只犬，通过插入胫跗关节附近右侧胫神经的针电极施加方波刺激（持续时间0.1毫秒，频率4赫兹）。通过确定在足底骨间肌诱发最大M波（肌肉诱发电位）所需的刺激，为每只犬建立标准刺激强度（参考有效刺激[RS]）。然后反转刺激电极的极性，并在T13 - L1弓间韧带水平记录SEP。随后，施加RS的分数倍（1/4x、1/2x）和倍数（2x、4x）的刺激。还对2只犬使用10x RS刺激进行记录；其中1只犬在箭毒化前后进行记录。在每种情况下，测量并评估前3个可重复偏转的潜伏期和振幅。
所有犬使用RS在T13 - L1水平记录的SEP波形相似；至少可识别出3个偏转。改变刺激强度并未显著改变前3个峰的潜伏期；相反，当刺激强度从1/4x RS增加到1x RS时，前3个峰的振幅增加（P < 0.01）。10x RS刺激诱发出一个大电位，该电位被箭毒化抑制。
在很宽的刺激强度范围内，只有轻微变化会影响潜伏期数据；潜伏期测量可被视为在RS附近的可靠工具。SEP记录过程中电极位置的轻微变化不应使结果无效。不同实验室之间刺激强度定义的差异不应妨碍结果的比较。
