Evaluation of Global Muscle Innervation Using Multi-Channel Surface Electromyography

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.