Application of the collision technique and development of fast-recovery preamplifier for detecting conduction delicits in lumbar spinal stenosis.

临床记录的外周神经刺激后的腰骶诱发电位对单个神经根损伤的敏感度低于预期。尽管直接神经根刺激有潜在的优势，但由于刺激伪影过多，它并不实用。碰撞技术应该可以绕过这些问题。对持续局部压迫造成的单个L-5神经根损伤大鼠，比较刺激坐骨神经(组1)和直接刺激L-5根(组2)后硬膜外记录电位的时序变化，并与L-6根和坐骨神经联合刺激(组3)后的结果进行比较。在记录的每一步，组2和组3的N1峰值幅度显著小于组1，而组2和组3之间没有显著差异。因此，组3中的碰撞技术通过阻断通过L6根传递的不需要的脉冲，获得了几乎与组2中直接L5根刺激相同的诊断率。在临床实践中，与动物实验不同，通过屏蔽刺激器与周围组织的刺激伪影，从而减少刺激电流的传播，很难控制刺激伪影。为了解决这个问题，我们研制了一种快速恢复前置放大器。这种插入在记录电极和放大器之间的前置放大器允许在大刺激输入的时刻打开传导路径，并随着其幅度的下降而关闭该路径。前置放大器的印制电路板由玻璃环氧树脂制成，这是因为该材料具有优异的高频特性。它被双重包裹在两个铝箱中，从而免受外部电气噪音的影响。此外，通过使用MCD-5221开关，开关闭合和断开时产生的电气噪声被降至最低。

Clinically recorded lumbosacral evoked potentials after peripheral nerve stimulation are less sensitive than might be expected for a single radicular lesion. Direct nerve root stimulation, despite its potential advantage, is not practical because of an overloading stimulus artifact. A collision technique should circumvent these problems. For a single L-5 radicular lesion produced in rats by constant, localized compression, sequential changes of epidurally recorded potentials after sciatic nerve stimulation (Group 1) or direct L-5 root stimulation (Group 2) were compared to those after a combination of L-6 root and sciatic nerve stimulation (Group 3). At every step of recording, the N1 peak amplitude was significantly smaller in group 2 and 3 than in group 1, whereas there was no significant difference between group 2 and 3. Thus, the collision technique in gourp 3 achieved nearly the same diagnostic yield as the direct L5 root stimulation in group 2 by blocking the unwanted impulses transmitted via the L6 root.In clinical practice, unlike animal experiments, it is difficult to control the stimulus artifact by shielding the stimulator from the surrounding tissues and thereby reducing spread of stimulus current. To circumvent this problem, we developed a fast-recovery preamplifier. This preamplifier interposed between the recording electrodes and the amplifier allows opening the conduction path at the moment of large stimulus input and closing the path with the wane of its magnitude. The printed circuit plate of the preamplifier was made of glass epoxy because of an excellent high frequency specificity of the material. It was shielded from the outside electric noise by being doubly encased in two aluminum boxes. In addition, the electric noise occurring when the switch closes and opens was minimized by using the MCD-5221 switch.