Quantification of shape changes observed in motor unit action potentials

Objective: It was aimed to develop an effective method for quantification of the shape variability (expressed as jiggle) observed in consecutive motor unit potentials (MUP), which can be used as an additional parameter in diagnosis and follow-up of neuromuscular pathologies in the clinic, and to examine the factors that cause these shape changes. Method: In order to calculate the CAD and CCC values used to quantify the jiggle term, an automatic analysis window selection algorithm was developed using the MUP median optimization. A noise correction algorithm has been developed using the sliding windows method to avoid the jiggle value from being affected by background noise and artifacts. To test the developed method, MUPs recorded from patients diagnosed with ALS (n = 190) and healthy individuals (n = 221) without any signs of neuromuscular pathology were used. In order to reveal neuromuscular factors affecting the jiggle term, MUP simulation was performed with the volume conductor model. Results: With the developed algorithm, MUP wave duration, the noise level and the intensity of the artifacts are automatically determined. The jiggle values obtained with the Modified method 5 % threshold value (CAD: 0.216 ± 0.008) and the Manual analysis window (CAD: 0.218 ± 0.006) are statistically significant for the ALS group. ALS and Control groups MUP waves are distinguished with 98.47% sensitivity and 98.64% specificity. Increased jitter time, the percentage of re-innervation and blocking cause a significant increase in jiggle value. The expansion of the motor endplate distribution causes a statistical increase in the MUP wave duration but does not affect the jiggle value. Conclusion: With the modifications proposed, neuromuscular jiggle can be quantified without being affected by wave duration and noise level. The jiggle value, which quantitatively expresses the state of a motor unit, has the potential to be a parameter for the diagnosis and follow-up of neuromuscular pathologies in the clinic.