P32.1 Distribution of regular and irregular firing patterns of denervation activity in completely denervated human muscle

Abstract

Background: It has been claimed that spontaneous activity from denervated muscle fibers (MFs) has a regular firing pattern (FP), though there is considerable disagreement regarding this claim. Aim/objective: The objective was to determine the distribution of firing patterns of denervated MFs. Patients and method: 553 FPs of individual fibrillation potentials or positive sharp waves from 182 recordings in 33 patients with completely denervated muscles were analyzed. Our own decomposition program EMGTools, originally developed for motor unit analysis, was used for extracting the FPs. This semi-automatic template matching method along with powerful visual tools for verifying the result enabled us to classify the FPs as being either regular or irregular. Each recording had a duration of 20 s.Most signals had 1–10 distinct potentials resulting in the same number of FPs. In some muscles a greater number of potentials occurred which made the analysis more difficult. Only FPs that could be visually confirmed as being full were included. Results: The variation in FPs and mean inter potential interval (IPI) was large across signals and patients. Fifty-seven percentage of the FPs was found to be regular, the rest of the FPs were identified as irregular. Amixture of regular and irregular FPs within the same recording was also found. Conclusion: Our investigation showed that about half of denervation potentials have irregular FPs.