Spasticity may defend skeletal muscle size and composition after incomplete spinal cord injury

Design: Cross-sectional. Objectives: (1) To determine the effects of the level of spinal cord injury (SCI) on skeletal muscle, intramuscular fat (IMF) cross-sectional areas (CSAs) and relative IMF; (2) to determine the relation, if any, of spasticity to each of these variables after incomplete SCI. Settings: In-patient study at the Shepherd Center, Atlanta, GA, USA. Methods: Thirteen individuals with incomplete SCI were classified according to their level of injury into a high level of injury group (HLI, C5-C7, n = 8) and a low level of injury group (LLI, T12-L2, n 5). Spasticity was determined for thigh muscles using a modified Ashworth scale at 6 weeks post-injury. T1-weighted magnetic resonance (MR) images were taken 6 weeks post-injury to measure thigh skeletal muscle and IMF CSAs. Results: Spasticity was significantly evident in the HLI group compared to the LLI group (P = 0.023). Six weeks post-injury, muscle CSA was 103 +/- 18 cm(2) in the HLI group and 80 +/- 20cm(2) in the LLI group (P = 0.042). Relative IMF was 3.6 +/- 2.0% in HLI and 7.5 +/- 4.0% in LLI (P = 0.021). Additionally, spasticity accounted for 54% of the variability in muscle CSA for all subjects (r(2) = 0.54, P = 0.006). Conclusions: Spasticity may be an important factor in defending skeletal muscle size and indirectly preventing IMF accumulation early after incomplete SCI.