Clinical Neurophysiology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
PLoS One. 2013 Jun 20;8(6):e67113. doi: 10.1371/journal.pone.0067113. Print 2013.
In common peripheral neuropathies, sensory symptoms usually prevail over motor symptoms. This predominance of sensory symptoms may result from higher sensitivity of sensory axons to ischemia.
We measured median nerve compound sensory action potentials (CSAPs), compound muscle action potentials (CMAPs), and excitability indices in five healthy subjects during forearm ischemia lasting up to disappearance of both CSAPs and CMAPs.
ISCHEMIA INDUCED: (1) earlier disappearance of CSAPs than CMAPs (mean ± standard deviation 30±5 vs. 46±6 minutes), (2) initial changes compatible with axonal depolarization on excitability testing (decrease in threshold, increase in strength duration time constant (SDTC) and refractory period, and decrease in absolute superexcitability) which were all more prominent in sensory than in motor axons, and (3) a subsequent decrease of SDTC reflecting a decrease in persistent Na(+) conductance during continuing depolarisation.
Our study shows that peripheral sensory axons are more vulnerable for ischemia than motor axons, with faster inexcitability during ischemia. Excitability studies during ischemia showed that this was associated with faster depolarization and faster persistent Na(+) channel inactivation in sensory than in motor axons. These findings might be attributed to differences in ion channel composition between sensory and motor axons and may contribute to the predominance of sensory over motor symptoms in common peripheral neuropathies.
在常见的周围神经病中，感觉症状通常比运动症状更为常见。这种感觉症状的优势可能是由于感觉轴突对缺血更为敏感所致。
我们在 5 名健康受试者中测量了正中神经复合感觉动作电位（CSAP）、复合肌肉动作电位（CMAP）和兴奋性指数，在持续到 CSAP 和 CMAP 均消失的前臂缺血期间。
缺血诱导：（1）CSAP 比 CMAP 更早消失（平均值±标准偏差 30±5 与 46±6 分钟），（2）在兴奋性测试中与轴突去极化一致的初始变化（阈值降低、强度持续时间常数（SDTC）和不应期增加，以及绝对超兴奋性降低），这些变化在感觉轴突中比在运动轴突中更为明显，（3）随后的 SDTC 降低反映了在持续去极化过程中持续的 Na+电导的降低。
我们的研究表明，周围感觉轴突比运动轴突对缺血更为敏感，在缺血期间更快地丧失兴奋性。缺血期间的兴奋性研究表明，这与感觉轴突比运动轴突更快的去极化和更快的持续 Na+通道失活有关。这些发现可能归因于感觉和运动轴突之间离子通道组成的差异，并可能导致常见周围神经病中感觉症状比运动症状更为常见。
