No abstract

No abstract

To use these reference values for repeated measurements, MF and MT can be corrected for either weight or height. It does not seem necessary to correct EI for these factors during follow-up of a few years. These results provide a basis for more precise detection of changes in muscle structure or force in neuromuscular disorders.

The purpose of this study was to identify optimal ways to detect neurogenic changes with high-density surface electromyography (HD-sEMG). For this purpose, we searched for the variables that most clearly discriminated between postpoliomyelitis and healthy subjects. We obtained HD-sEMG from the quadriceps muscle at different force levels in nine subjects with postpoliomyelitis syndrome and in matched healthy controls. Single motor unit action potentials (MUAPs), extracted from the HD-sEMG signal and the raw signal itself, were analyzed. Areas under the curve of the extracted MUAP waveform, indicating motor unit size, perfectly separated both groups. Raw signal analysis showed significant differences between groups for the monopolarly recorded amplitude up to 60% of maximal force and for the level of interference at higher force levels (40-100% force). We conclude that with HD-sEMG it is possible to detect neurogenic motor unit changes noninvasively, both by analysis of the raw signal itself and by analysis of extracted single MUAPs. The diagnostic yield of the single MUAP analysis is clearly higher. These findings point toward applications for clinical practice and invite further studies exploring the diagnostic value of HD-sEMG.

In amyotrophic lateral sclerosis (ALS), progressive motor neuron loss causes severe weakness. Functional measurements tend to underestimate the underlying pathology because of collateral reinnervation. A more direct marker of lower motor neuron loss is of significant importance. We evaluated high-density motor unit number estimation (MUNE), as compared with the ALS Functional Rating Scale (ALSFRS) and maximal compound muscle action potential (CMAP) amplitude, for monitoring and classifying disease progression. MUNE showed good reproducibility (intraclass correlation coefficient = 0.86). MUNE showed a significantly greater decrease than the ALSFRS, the Medical Research Council (MRC) scale, and CMAP amplitude. Patients could be stratified into groups with rapidly or slowly progressive disease based on a decrement in MUNE at 4 months from baseline; ALSFRS score at 8 months was significantly lower in the rapidly progressive group. MUNE was sensitive to motor neuron loss early in the disease course when compared to other clinical measures. Stratification of patients based on a decrease in MUNE seems feasible.