Zhang Guanghao, Zhang Cheng, Wu Changzhe, Huo Xiaolin
Beijing Key Laboratory of Bioelectromagnetism, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, P.R.China.
School of Electronics, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, P.R.China.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2021 Apr 25;38(2):232-240. doi: 10.7507/1001-5515.202007016.
Spinal cord stimulation (SCS) for pain is usually implanted as an open loop system using unchanged parameters. To avoid the under and over stimulation caused by lead migration, evoked compound action potentials (ECAP) is used as feedback signal to change the stimulating parameters. This study established a simulation model of ECAP recording to investigate the relationship between ECAP component and dorsal column (DC) fiber recruitment. Finite element model of SCS and multi-compartment model of sensory fiber were coupled to calculate the single fiber action potential (SFAP) caused by single fiber in different spinal cord regions. The synthetized ECAP, superimposition of SFAP, could be considered as an index of DC fiber excitation degree, because the position of crests and amplitude of ECAP corresponds to different fiber diameters. When 10% or less DC fibers were excited, the crests corresponded to fibers with large diameters. When 20% or more DC fibers were excited, ECAP showed a slow conduction crest, which corresponded to fibers with small diameters. The amplitude of this slow conduction crest increased as the stimulating intensity increased while the amplitude of the fast conduction crest almost remained unchanged. Therefore, the simulated ECAP signal in this paper could be used to evaluate the degree of excitation of DC fibers. This SCS-ECAP model may provide theoretical basis for future clinical application of close loop SCS base on ECAP.
用于疼痛治疗的脊髓刺激（SCS）通常作为一个使用不变参数的开环系统植入。为避免因电极迁移导致的刺激不足和过度刺激，诱发性复合动作电位（ECAP）被用作反馈信号来改变刺激参数。本研究建立了一个ECAP记录的仿真模型，以研究ECAP成分与背柱（DC）纤维募集之间的关系。将SCS的有限元模型与感觉纤维的多节段模型相耦合，以计算不同脊髓区域中单根纤维引起的单纤维动作电位（SFAP）。合成的ECAP，即SFAP的叠加，可被视为DC纤维兴奋程度的指标，因为ECAP的波峰位置和幅度对应于不同的纤维直径。当10%或更少的DC纤维被兴奋时，波峰对应于直径较大的纤维。当20%或更多的DC纤维被兴奋时，ECAP显示出一个慢传导波峰，其对应于直径较小的纤维。随着刺激强度增加，这个慢传导波峰的幅度增加，而快传导波峰的幅度几乎保持不变。因此，本文中的模拟ECAP信号可用于评估DC纤维的兴奋程度。这个SCS-ECAP模型可能为基于ECAP的闭环SCS未来临床应用提供理论依据。
