中文摘要：

临床研究证实,硬膜外脊髓电刺激（ESCS）能促进脊髓损伤后的运动功能恢复,但基本神经机制则需通过动物实验进行研究.在建立大鼠ESCS有限元-神经元组合模型的基础上,仿真L2节段单阴极刺激条件下脊髓组织内的电势分布,确定L1到S1节段背根、腹根纤维和不同深度背柱纤维激活阈值的变化规律,分析纤维位置和刺激脉宽对神经纤维激活阈值的影响.仿真结果发现,距电极最近的背根纤维激活阈值最低为0.41 V,浅层背柱纤维的激活阈值略高为0.47 V,最近腹根纤维的激活阈值最高为0.78 V,减小电极-纤维距离有利于脊髓纤维的选择性激活;不同深度背柱纤维的激活阈值随刺激脉宽增加而减小,但脉宽过大导致背柱纤维激活阈值的降幅变小,过长的脉宽使得激活阈值的降幅趋缓,合理选择刺激脉宽有利于激活深层背柱纤维,增加脊髓组织的激活区域,提高ESCS对于深层背柱纤维的募集能力.该仿真结果可为动物实验研究中合理选择刺激参数、提高刺激选择性能提供理论指导.

英文摘要：

Clinical research demonstrated that epidural spinal cord stimulation （ESCS） was able to facilitate motor function recovery after spinal cord injury, but the underlying neural mechanism must be explored by animal experiments. In this paper, based on the construction of finite element and neuron model of ESCS, the distribution of electric potentials was simulated in the rat spinal cord with a stimulating cathode located at the midpoint of L2 spinal segment. The excitation thresholds of typical spinal fibers were calculated to analyze the influence of the fiber location and pulse width on the recruitment of nerve fibers. The simulation results showed that the dorsal root fiber entering the spinal cord at the cathode level had the lowest excitation threshold of 0. 41 V, whereas the excitation threshold of the ventral root fiber at the same level was 0.78 V and much higher than that of the most superficial dorsal column fiber with the excitation threshold of 0.47 V. The decrease of the fiber-electrode distance was able to improve the selectivity of fiber activation. It was also shown that the excitation threshold of dorsal column fibers at different depths within the midsagittal plane of spinal cord decreased with the increase of pulse width, whereas too long pulse width corresponded to the decreased slope of the varied activation threshold for dorsal column fibers. Therefore, the choice of an appropriate pulse width isessential to the activation of deep dorsal column fibers and the increasing activated area Our simulation results would offer guidance for the selection of stimulation parameters the stinmlation selectivity during animal experiments. of the stimulated tissue and the improvement of