Graduate School of Engineering Science, Department of Mechanical Science and Bioengineering, Osaka University, Toyonaka, Osaka, Japan.
Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Artif Organs. 2022 Oct;46(10):2015-2026. doi: 10.1111/aor.14323. Epub 2022 Jun 7.
Cervical transcutaneous spinal cord stimulation (tSCS) is a rehabilitation tool which has been used to promote upper-limb motor recovery after spinal cord injury. Importantly, optimizing sensory fiber activation at specific spinal segments could enable activity-dependent neuromodulation during rehabilitation.
An anatomically realistic cervical tSCS computational model was used to analyze the activation of α-motor and Aα-sensory fibers at C7 and C8 spinal segments using nine cathode electrode configurations. Specifically, the cathode was simulated at three vertebral level positions: C6, C7, and T1; and in three sizes: 5.0 × 5.0, 3.5 × 3.5, and 2.5 × 2.5 cm , while the anode was on the anterior neck. Finite element method was used to estimate the electric potential distribution along α-motor and Aα-sensory fibers, and computational models were applied to simulate the fiber membrane dynamics during tSCS. The minimum stimulation intensity necessary to activate the fibers (activation threshold) was estimated and compared across cathode configurations in an effort to optimize sensory fiber activation.
Our results showed that nerve fibers at both C7 and C8 spinal segments were recruited at lower stimulation intensities when the cathode was positioned over the C7 or T1 vertebra compared with the C6 position. Sensory fibers were activated at lower stimulation intensities using smaller electrodes, which could also affect the degree of nerve fiber activation across different positions. Importantly, Aα-sensory fibers were consistently recruited before α-motor fibers.
These results imply that cathode positioning could help optimize preferential activation of hand muscles during cervical tSCS.
经皮脊髓刺激（tSCS）是一种康复工具，已被用于促进脊髓损伤后的上肢运动恢复。重要的是，优化特定脊髓节段的感觉纤维激活可在康复过程中实现活动依赖性神经调节。
使用解剖学上逼真的颈 tSCS 计算模型，使用 9 种阴极电极配置分析 C7 和 C8 脊髓节段的α运动和 Aα感觉纤维的激活。具体来说，阴极在三个椎骨水平位置（C6、C7 和 T1）和三个尺寸（5.0×5.0、3.5×3.5 和 2.5×2.5 cm）进行模拟，而阳极位于颈部前侧。有限元法用于估计α运动和 Aα感觉纤维的电位分布，并应用计算模型模拟 tSCS 期间纤维膜动力学。估计并比较了在不同阴极配置下激活纤维所需的最小刺激强度（激活阈值），以优化感觉纤维的激活。
我们的结果表明，与 C6 位置相比，当阴极位于 C7 或 T1 椎骨上时，C7 和 C8 脊髓节段的神经纤维在较低的刺激强度下被募集。使用较小的电极可在较低的刺激强度下激活感觉纤维，这也会影响不同位置的神经纤维激活程度。重要的是，Aα感觉纤维始终在α运动纤维之前被募集。
这些结果表明，阴极定位有助于优化颈 tSCS 期间对手部肌肉的优先激活。
