Restoring Motor Function in Long-Term Paralyzed Muscles: Insights from Experimental and Clinical Evidence on Peripheral Nerve Reconstruction

Tel Aviv University, Tel Aviv, Israel Assuta Medical Center, Tel Aviv, Israel

BACKGROUND: The neurosurgical reconstruction approach has traditionally been considered ineffective for long-term paralyzed muscles following peripheral nerve injury due to the extensive degeneration and reduced regenerative capacity of chronically denervated muscles. This belief stems from challenges in achieving functional reinnervation and restoring muscle activity after prolonged periods of denervation. However, findings presented in this study would suggest a shift in this perspective. This study integrates findings from both experimental research on rats and a clinical case report to propose that peripheral nerve reconstruction can be a viable method for regaining motor function even in long term paralyzed muscle.

METHODS: 1. Experimental Study: Conducted on 48 rats, where the gastrocnemius muscle was denervated by removing a 10mm segment of the sciatic nerve. Acetylcholine receptors (AChR) and creatine kinase (CK) activity were measured at 7, 14, and 21 days, and 1, 2, 4, and 7-months post-denervation. AChR levels were quantified using 125I-α-bungarotoxin, and CK activity was assessed spectrophotometrically. 2. Clinical Case Report: Involved one patient (aged 5 years) with severe elbow flexion disability from late obstetrical Erb’s palsy. End-to-side anastomosis of intact ulnar nerve fascicles into the barely functional musculocutaneous nerve was performed. Pre- and postoperative motor function evaluation was conducted over an 18-year follow-up period.

RESULTS: 1. Experimental Study: Progressive degradation of AChR and CK content was observed post-denervation. Notably, partial preservation of these components was seen up to 7 months, suggesting potential for reinnervation. 2. Clinical Case Report: Along 18 years postoperative follow up, elbow flexion strength has improved from M1 to M5-. Electrophysiological assessments showed enhanced compound muscle action potentials and recruitment.

CONCLUSION: The combined evidence from animal models and clinical case suggests that peripheral nerve reconstruction has the potential to restore motor function even in long-term denervated muscles.