Concentric single fiber electromyography parameters in neuromuscular junction and muscle diseases and reinnervation models

Introduction: Single fiber electromyography (SFEMG) is an advanced electromyography method used for the diagnosis of neuromuscular junction diseases. With SFEMG, not only jitter analysis, but also fiber density can be calculated, and it increases in diseases that change the motor unit architecture. Today, it is recommended to prefer a disposable concentric needle with a narrow recording surface (25 mm, 30 G) instead of the original needle electrode. However, an equivalent concept of "fiber density" has not been defined for this needle. Objective: The aim of this study is to calculate jitter values, block rates and spike number in disease models that change the motor unit architecture as well as primary junction diseases with the newly proposed concentric needle electrode and to reveal the distinctive features in these diseases. Method: 15 Myasthenia Gravis, 13 myopathy and 13 motor neuron patients were included in this study. SFEMG and spike number were measured during voluntary muscle contraction using a concentric needle electrode from the frontalis muscle in 24 volunteers and MG patients, and from the extensor digitorum communis muscle in 15 volunteers and myopathy and motor neuron patients. Results: The mean jitter value was 49.42±21.89 µs in MG patients and 18.34±2.51 µs in volunteers, 22.98±5.95 µs in myopathy patients, 63.48±23.76 µs in motor neuron patients and 21.99±2.29 µs in volunteers. The mean spike number value was 2.90±0.52 in MG patients and 2.31±0.18 in volunteers, 3.51±0.46 in myopathy patients, 4.79±1.12 in motor neuron patients, and 2.30±0.15 in volunteers. No block was found in healthy volunteers. The rate of block was 40% in MG patients, 15.4% in myopathy patients, and 61.5% in motor neuron patients. Conclusion: The mean jitter and spike number values were highest in motor neuron patients. The jitter value was the lowest in myopathy patients, and the spike number value was the lowest in MG patients. The block rate was highest in motor neuron patients and lowest in myopathy patients.