Purpose of review: Clinical investigations of neuromuscular diseases routinely involve genetic, neurophysiological, biochemical and histopathological methods. More recently, various magnetic resonance imaging techniques have become available and extended the differential diagnostic possibilities.
Recent findings: Using magnetic resonance imaging it is now possible to quantify muscle volume in selected body regions and measure wasting and exercise-induced muscle hypertrophy. Evidence is forthcoming that many hereditary myopathies are characterized by distinct patterns of muscle degeneration and this helps in selecting other relevant genetic and biochemical investigations. With diffusion-weighted tensor imaging it is possible to identify the microstructure of normal and diseased muscles. Arterial spin labelling is an emerging non-invasive tool to assess blood-flow changes in individual muscles. Magnetic resonance spectroscopy now provides an exciting opportunity to visualize metabolic changes and the pathophysiologically relevant cellular perturbations in muscle channelopathies affecting the muscle-specific sodium-channel isoform Na(v)1.4.
Summary: Magnetic resonance imaging supplements investigations for the differential diagnosis of neuromuscular diseases. An advantage over routine neurophysiological or histopathological methods is that they are operator-independent, non-invasive and painless. Magnetic resonance imaging also has the advantage of providing a lasting detailed topographical picture of regional variations and allows robust measurements of muscle volume and various functional parameters.