O10: Effect size of quantitative muscle imaging in Duchenne muscular dystrophy exceeds the effect size of clinical scores of muscle function

Abstract

s of Oral Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 S31 confirmed Duchenne muscular dystrophy. Physical assessment was performed using the motor function measurement (MFM) scale. Quantitative magnet resonance imaging (qMRI) of thigh muscles was performed using the two-point Dixon method. One year functional and imaging changes were different according to the age and walking abilities at inclusion (group 1: below the age of seven; group 2: seven years and older and ambulant; group 3: non-ambulant). While patients of the first group still showed improvement of motor abilities, in group 2 the largest effect size (1.2) was found in the D1 subscore (standing and transfer function) of the MFM, and in group 3 the largest effect size was found for the total MFM score (0.66). In contrast, the effect sizes using qMRI was much larger consisting of 1.6 in group 1 (all thigh muscles), 4.1 in group 2 (hamstrings), and 2.3 in group 3 (knee extensors). These data suggest that qMRI has an added value compared to clinical outcome measures when designing therapeutic clinical trials in patients with DMD. Power analysis suggest that there are only a few needed patients to show an effect of a putative novel treatment when using quantitive muscle MRI in DMD. O11 Estimation of the muscle fiber density from the motor unit action potential I. Goker1, T. Artug2, O. Osman2, B. Baslo3 1Istanbul Arel University, Biomedical Engineering, Istanbul, Turkey; 2Istanbul Arel University, Electrical and Electronics Engineering, Istanbul, Turkey; 3Istanbul University, Medical Faculty, Istanbul, Turkey Introduction: The aim of this study is the estimation of the muscle fiber density (FD) from the Motor Unit Action Potentials (MUAP) to form a method for monitoring the progress of neuromuscular diseases. Methods: Data groups representing motor units of neurogenic (n=5), myopathic (n=5) and healthy cases (n=5) were created via EMG Simulator v3.6. MUAPs generated from each data group have been detected through a concentric needle electrode of a scanning EMG system. The spikes of the single fiber action potentials within the MUAPs have been found by computing the second-order derivative of MUAPs to estimate the detected number of fibers. MUAPs from 20 different locations within a Motor Unit Territory (MUT) have been acquired. The fiber density (FD) has been computed by taking the average of these numbers of fibers. True FDs have been computed for each MUT. Mean Square Errors (MSE) have been computed for each data group to determine the sensitivity of the method. Results: The test statistics of the FDs (mean ± SD) have been found as 4.13±1.31 (Min: 2 and Max: 8), 2.37±0.98 (Min: 1 and Max: 5) and, 2.40±0.70 (Min: 1 and Max: 4) for neurogenic, myopathic and healthy cases respectively. Mean true fiber densities have been 5.66, 2.57 and 1.50 and MSE have been 4.02, 0.15 and, 0.86 for neurogenic, myopathic and healthy cases respectively. These MSE values have been suggested that this method is more selective for myopathic cases compared to neurogenic and healthy cases. Conclusion: Computation of FD via the second-order derivative of MUAPs can be considered as a beneficial preliminary research. Nevertheless, this method might be extended by taking into account other variables such as maximum amplitude to increase the sensitivity for neurogenic cases.