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

Abstract

Study Design: Cross-sectional study. Objective: (1) To quantify intramyocellular lipid (IMCL) content of the soleus muscle. (2) To assess the T 2 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. T 2 -weighted imaging of lower extremity muscles yielded muscle T 2 rates. Results: The IMCL content of the soleus muscle was 3.3 times higher in the patient group as compared to controls (P ¼ 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 ¼ 0.002). Significant differences were observed in the T 2 relaxation times of the soleus and gastrocnemius muscles (Po0.05). 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 T 2 relaxation times of the locomotor muscles are reflective of an altered muscle composition.

Hindlimb Muscle Morphology and Function in a New Atrophy Model Combining Spinal Cord Injury and Cast Immobilization

“…In the SCI + IMM group, the addition of cast immobilization minimized the loading on the muscle, allowing for examination of the role of neuromuscular activity and/or loading in the muscle adaptations after SCI. This model is more consistent with what is generally observed in human complete or chronic incomplete SCI, [39][40][41][42] in which patients usually experience an extended period of bed rest and reduced activity during the acute phase of the injury, up to several weeks. The primary muscles of ambulation continue to experience reduced loading for several weeks to months after SCI as activity-based rehabilitation is delayed by other posttraumatic complications.…”

Myofibrillar distribution of succinate dehydrogenase activity and lipid stores differs in skeletal muscle tissue of paraplegic subjects

“…Using nuclear magnetic resonance, previous studies have reported increased intramuscular lipid content in deconditioned leg muscles of PAR individuals (21,23,55). In addition, an initial reduction of muscle mitochondrial oxidative activity has been observed directly after spinal cord injury, followed by a recovery to nearly normal levels after 6 mo (13).…”

Magnetic Resonance Imaging: The Underlying Principles

“…The ability to monitor in vivo spectral changes has a range of clinical applications for the musculoskeletal system, including monitoring intracellular and extracellular fat changes, 31 exercise-induced changes in metabolites, 14 intracellular pH abnormalities in chronic fatigue syndrome, 22 and examining muscular response to neurological insult and/or disuse through intramyocellular lipid content 33 or changes in inorganic phosphate. 26,27 SPATIAL ENCODING I n addition to chemical information, the signal can be encoded with spatial position and used to obtain an image.…”