MRI of normal and pathologic skeletal muscle

Lower extremity skeletal muscle of 22 individuals (five normal volunteers and 17 patients with muscular or neuromuscular diseases) was studied with magnetic resonance imaging. Axial images generated with spin-echo pulse sequences using short repetition times (500-900 msec TR) and short echo times (30-60 msec TE) provided excellent contrast between fat (high signal intensity) and muscle (intermediate signal intensity). Seventeen patients with clinically verified muscle disorders were evaluated in a manner similar to the normal volunteers. Conditions studied include Duchenne muscular dystrophy (three patients), limb-girdle muscular dystrophy (five), facioscapulohumeral dystrophy (three), and spinal muscular atrophy, amyotrophic lateral sclerosis, hereditary sensorimotor neuropathy, cerebral palsy, poliomyelitis, and Kearn-Sayre mitochondrial muscle disease (one each). General patterns of muscle abnormality were common among the diseases and included decreased or increased muscle size and a spectrum of muscle replacement by fat. Variable patterns were observed within disease groups and for each patient. Much phosphorus-31 spectroscopy has been performed in a blind fashion with no proton map of normal/abnormal muscle distribution to guide the spectroscopist. This study emphasizes the worth of having a muscle proton map of patients with muscle dysfunction to assure that meaningful phosphorus spectroscopic information is obtained from a volume of tissue limited to an appropriate muscle.