Jitter evaluation in denervation and reinnervation in 32 cases of chronic radiculopathy.

Objective: To measure the jitter parameters in muscles with denervation/reinnervation in 32 chronic radiculopathy cases.

Methods: Measurements were done in chronic denervated muscles by voluntary and electrical activation using a concentric needle electrode.

Results: Mean jitter was abnormal in 87.5% (mean 49.2 µs) and 81.25% (mean 36.8 µs), for voluntary and electrical activation. In muscles with fibrillation potentials (FPs), the mean jitter was abnormal in all cases, and impulse blocking was frequent (53.4-92.3%). In muscles without FPs, the mean jitter was abnormal in 78.9% for voluntary activation and 68.4% for electrical activation. No correlation was found between jitter and motor unit action potential amplitude.

Conclusion: The muscles with FPs were associated with the immature spread of acetylcholine receptors (AChRs) throughout the muscle membrane. Conversely, the neuromuscular junctions (NMJs) assemble may be repressed by the already reinnervated muscles. For those, higher jitter may be due to the persistence of atrophic fibers expressing neonatal myosin heavy chain (MHC) and immaturity of NMJ composting instead of the overspread of immature AChRs.

Significance: Jitter measurement must be avoided in chronic denervated muscles, regardless of FPs' presence. The activity of reinnervated muscle could maintain neonatal MHC and repress new NMJs development.