Skeletal muscle atrophy and increased intramuscular fat after incomplete spinal cord injury

Study design: Cross-sectional and longitudinal design. Objectives: ( 1) To quantify skeletal muscle cross-sectional area ( CSA) after correcting for intramuscular fat ( IMF) in thigh muscle groups 6 weeks after incomplete spinal cord injury ( SCI), ( 2) to monitor the changes in muscle CSA and IMF after 3 months from the initial measurement. Setting: Academic institution Athens, GA, USA. Methods: Six incomplete SCI patients ( 28 +/- 4 years, 178 +/- 5 cm and 78 +/- 6 kg, mean +/- SE, C7 to L3, American Spinal Injury Association B or C) were tested at 5 +/- 1 weeks and 3 months after the initial measurement. T1-weighted magnetic resonance images were taken of both thighs. Six able-bodied ( AB) controls were matched in age, sex, height and weight ( 29 +/- 4 years, four male and two female subjets, 179 +/- 5 cm and 77 +/- 6 kg). Results: At 6 weeks post-injury, muscle CSA was 82 +/- 4 cm(2) in incomplete SCI and 123 +/- 21 cm(2) in AB controls ( P = 0.04). IMF CSA was 5.2 +/- 1.3 and 2.3 +/- 0.6 cm(2) in incomplete SCI and AB controls, respectively ( P = 0.03). Relative IMF was three-fold higher ( P = 0.03) in the SCI group versus AB controls ( 5.8 +/- 1.4 versus 2.0 +/- 0.6%). After 3 months, IMF increased 26% in the SCI group compared to the initial measurement ( P = 0.02). Conclusions: Skeletal muscle atrophy is associated with greater IMF accumulation in SCI group 6 weeks post-injury compared to AB controls. Moreover, IMF continues to increase over time in incomplete SCI.