Muscle edema in MR imaging of neuromuscular diseases.

Muscle edema has been described as a typical finding on MR images in acute neuromuscular disorders, predominantly in acute inflammatory myopathies, but also in neuro- and myopathies. The purpose of this study was to examine the frequency of muscle edema and the diagnostic usefulness of Gd-DTPA in neuromuscular diseases. 144 consecutive patients with various generalized neuromuscular diseases were examined by MR imaging. Areas of high signal intensity, relative to normal muscle, were seen in 36% of T2-weighted images, whereas the corresponding T1-weighted images showed normal or lower signal intensities. These edema-like abnormalities--enlargement of the extracellular fluid space--were found more often in inflammatory and metabolic myopathies, but were also seen in degenerative myopathies. Contrast-enhanced T1-weighted images in 25 patients were not more sensitive than plain T2-weighted images.