Three-dimensional quantitative muscle ultrasound in patients with facioscapulohumeral dystrophy and myotonic dystrophy

Introduction/AimsUltrasound imaging of muscle tissue conventionally results in two-dimensional sampling of tissue. For heterogeneously affected muscles, a sampling error using two-dimensional (2D) ultrasound can therefore be expected. In this study, we aimed to quantify and extend ultrasound imaging findings in neuromuscular disorders by using three-dimensional quantitative muscle ultrasound (3D QMUS). MethodsPatients with facioscapulohumeral dystrophy (n = 31) and myotonic dystrophy type 1 (n = 16) were included in this study. After physical examination, including Medical Research Council (MRC) scores, the tibialis anterior muscle was scanned with automated ultrasound. QMUS parameters were calculated over 15 cm of the length of the tibialis anterior muscle and were compared with a healthy reference data set. ResultsWith 3D QMUS local deviations from the healthy reference could be detected. Significant Pearson correlations (P < .01) between MRC score and QMUS parameters in male patients (n = 23) included the mean echo intensity (EI) (0.684), the standard deviation of EI (0.737), and the residual attenuation (0.841). In 91% of all patients, mean EI deviated by more than 1 standard deviation from the healthy reference. In general, the proportion of muscle tissue with a Z score >1 was about 50%. DiscussionIn addition to mean EI, multiple QMUS parameters reported in this study are potential biomarkers for pathology. Besides a moderate correlation of mean EI with muscle weakness, two other parameters showed strong correlations: standard deviation of EI and residual attenuation. Local detection of abnormalities makes 3D QMUS a promising method that can be used in research and potentially for clinical evaluation.