Guangdong Work Injury Rehabilitation Center, Guangzhou 510440, China; Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611, USA.
Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611, USA; Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
Clin Neurophysiol. 2020 Jun;131(6):1407-1418. doi: 10.1016/j.clinph.2020.02.009. Epub 2020 Mar 3.
To determine limb differences in motor axon excitability properties in stroke survivors and their relation to maximal electromyographic (EMG) activity.
The median nerve was stimulated to record compound muscle action potentials (CMAP) from the abductor pollicis brevis (APB) in 28 stroke subjects (57.3 ± 7.5 y) and 24 controls (56.7 ± 9.3 y).
Paretic limb axons differed significantly from non-paretic limb axons including (1) smaller superexcitability and subexcitability, (2) higher threshold during subthreshold depolarizing currents, (3) greater accommodation (S3) to hyperpolarization, and (4) a larger stimulus-response slope. There were smaller differences between the paretic and control limbs. Responses in the paretic limb were reproduced in a model by a 5.6 mV hyperpolarizing shift in the activation voltage of Ih (the current activated by hyperpolarization), together with an 11.8% decrease in nodal Na conductance or a 0.9 mV depolarizing shift in the Na activation voltage. Subjects with larger deficits in APB maximal voluntary EMG had larger limb differences in excitability properties.
Stroke leads to altered modulation of Ih and altered Na channel properties that may be partially attributed to a reduction in neuromuscular activation.
Plastic changes occur in the axon node and internode that likely influence axon excitability.
确定脑卒中幸存者运动轴突兴奋性特征的肢体差异及其与最大肌电图（EMG）活动的关系。
刺激正中神经，记录 28 名脑卒中患者（57.3±7.5 岁）和 24 名对照者（56.7±9.3 岁）的拇短展肌（APB）复合肌肉动作电位（CMAP）。
患侧肢体轴突与健侧肢体轴突存在显著差异，包括：（1）超兴奋性和亚兴奋性较小；（2）阈下去极化电流时阈值较高；（3）超极化时适应（S3）较大；（4）刺激-反应斜率较大。患侧和健侧肢体之间的差异较小。在模型中，通过将 Ih 的激活电压（由超极化激活的电流）向超极化方向移动 5.6 mV，同时将节点 Na 电导降低 11.8%或 Na 激活电压向去极化方向移动 0.9 mV，可再现患侧肢体的反应。APB 最大自主 EMG 缺陷较大的患者，其兴奋性特征的肢体差异较大。
脑卒中导致 Ih 调制改变和 Na 通道特性改变，这可能部分归因于神经肌肉激活减少。
轴突节和节间发生了可塑性变化，可能会影响轴突兴奋性。
