Effect of heat on conduction study of the peripheral nerve : Measuring conduction block and distribution of velocities of the sensory nerve

由于与感觉障碍和不适相关的知觉和情绪存在个体差异，周围神经病变引起的感觉障碍难以准确评估。然而，在康复医学领域，还需要证明热如微波和超声对感觉障碍和不适的治疗作用。其作用机制也有待进一步研究。因此，我们开发了一种方法，通过在常规神经传导研究中获得的神经动作电位来指示感觉神经功能。通过求解所谓的逆问题，用数学方法估计了感觉神经传导速度的分布和传导阻滞的大小。我们成功地使用了一个手套状的接地电极，这种电极是由导电布制成的，这是数学分析所必需的。计算机模拟研究表明，当噪声小于30dB，传导阻滞幅度小于50%时，可以进行准确的估计。在2名健康受试者中验证了方法的重现性和有效性。两名受试者在微波或超声作用前后均未见波形变化。因此，我们记录了两名受试者在冰冻至25℃后手臂升温至35℃时的体温和电位。在1 ~ 1.3 m/s/℃范围内，速度随温度的升高呈线性增长。传导阻滞几乎以2-3%/℃的速率随温度升高而增加，这可能产生热治疗效果。最后，我们展示了这种评估方法在轻度糖尿病神经病变患者中的可能应用。

It is difficult to accurately evaluate sensory disturbance caused by peripheral nerve lesion because of individual difference in perception and emotion related to sensory disturbance and discomfort. It is nevertheless needed in the field of rehabilitation medicine to show therapeutic effects of heat such as microwave and ultrasound on sensory disturbance and discomfort. Mechanism of its efficacy also should be investigated. Thus, we developed a method to indicate sensory nerve function from nerve action potentials obtained during conventional nerve conduction studies. Distribution of sensory nerve conduction velocities and magnitude of conduction block were estimated mathematically by solving so-called inverse problems. We succeeded in noise-reduction of recorded potentials using a glove-shaped ground electrode made of electro-conducting cloth that was necessary for mathematical analysis. Computer simulation studies showed accurate estimation was possible when the noise was less than 30dB and the magnitude of conduction block was less than 50%. Reproducibility and validity of the method was checked in 2 healthy subjects. We could not see waveform changes between recorded potentials before and after application of either microwave or ultrasound in 2 subjects. Therefore, we recorded temperature and potentials while warming arms of the 2 subjects up to 35℃ after iced down to 25℃. Velocities increased with temperature in linear manner at 1-1.3 m/s/℃. Conduction block increased with temperature nearly at the rate of 2-3%/℃ which might yield therapeutic effects of heat. Finally, we showed possible application of this evaluation method for patients with mild diabetic neuropathy.