Evaluation of Global Muscle Innervation Using Multi-Channel Surface Electromyography

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Introduction: Advances in multi-channel surface electromyography (sEMG) have enabled the non-invasive assessment of neuromuscular function at the muscle and motor unit level. Specifically, sEMG has been used to assess the location of innervation zones (IZs) and the quantity of functioning innervation of targeted muscles. This knowledge associated with muscle innervation is critical to the clinical understanding, diagnosis and management of neuromuscular disorders, yet it remains an unmet need in both technical and clinical terms.

Methods: For the first part of the dissertation, a novel three dimensional IZ imaging (3DIZI) technique was introduced to map the IZ territory in the three dimensional muscle space, by incorporating high-density sEMG recording and decomposition, finite element method and electrical source imaging. This technique have been validated and employed to optimize the clinical management of post-stroke spasticity. While being precise and reliable, the IZ imaging technique is computationally demanding and time consuming. To this end, an improved IZ imaging approach was implemented by employing electrically evoked muscle potential. For the second part, a motor unit number estimation technique for pelvic muscles was established in a female rat model. The technique combines intra-vaginal stimulation, multi-channel intra-rectal surface EMG recording and statistical estimation.

Results: The proposed IZ imaging technique has demonstrated high accuracy, reliability and robustness to spastic conditions. Our clinical trial showed higher treatment effectiveness of botulinum neurotoxin in imaging-guided injection group. IZ imaging using electrically elicited compound muscle action potential can greatly reduce computational demand. Furthermore, we have for the first time, provided the feasibility of estimating the motor unit number of pelvic muscles, with accuracy validated by immune-histochemical staining.

Conclusions: The three dimensional IZ imaging and motor unit number estimation technique have provided novel tools for the assessment of global neuromuscular innervation in muscles. The promising results and validation of technique have laid out solid foundation for future clinical application.

Surface electromyography, Multi-channel, Innervation zone, Muscles, Motor unit number estimation, Motor functions
Portions of this document appear in: Zhang, Chuan, Yen-Ting Chen, Yang Liu, Ping Zhou, Sheng Li, and Yingchun Zhang. "Three dimensional innervation zone imaging in spastic muscles of stroke survivors." Journal of neural engineering 16, no. 3 (2019): 034001. And in: Zhang, Chuan, Yun Peng, Yang Liu, Sheng Li, Ping Zhou, William Zev Rymer, and Yingchun Zhang. "Imaging three-dimensional innervation zone distribution in muscles from M-wave recordings." Journal of neural engineering 14, no. 3 (2017): 036011. And in: Zhang, Chuan, Nicholas Dias, Jinbao He, Ping Zhou, Sheng Li, and Yingchun Zhang. "Global Innervation Zone Identification with High-Density Surface Electromyography." IEEE Transactions on Biomedical Engineering (2019). And in: Zhang, Chuan, Alvaro Munoz, H. Henry Lai, Timothy Boone, and Yingchun Zhang. "Non‐invasive electromyographic estimation of motor unit number in the external anal sphincter of the rat." Neurourology and urodynamics 37, no. 1 (2018): 115-122.