Non-invasive assessment of lower extremity muscle composition after incomplete spinal cord injury

Study Design: Cross-sectional study. Objective: (1) To quantify intramyocellular lipid (IMCL) content of the soleus muscle. (2) To assess the T₂ relaxation rates in the lower extremity skeletal muscles in persons with incomplete spinal cord injury (SCI). Setting: Academic Institution, Florida. Methods: Eight subjects (42±10 years old; 70±12 kg; 176±10 cm) with chronic (17±9 months post injury) motor SCI (C4-T12; ASIA C or D) and eight matched healthy controls were tested. Localized unsuppressed proton spectroscopy (H-MRS) was performed to estimate total lipid content and individual lipid components; IMCL and extramyocellular lipid (EMCL) from the soleus muscle. T₂-weighted imaging of lower extremity muscles yielded muscle T₂ rates. Results: The IMCL content of the soleus muscle was 3.3 times higher in the patient group as compared to controls (P=0.002; 0.0401 (0.0234-0.0849) versus 0.0123 (0.0090-0.0175)). Similarly, EMCL measures were 4.5 times higher as compared to the controls (P=0.002). Significant differences were observed in the T₂ relaxation times of the soleus and gastrocnemius muscles (P<0.05). Conclusion: The increased levels of IMCL might interfere with the glucose uptake in skeletal muscle; potentially predisposing persons with incomplete SCI to the development of peripheral insulin resistance. Marked elevations in the T₂ relaxation times of the locomotor muscles are reflective of an altered muscle composition.