Influence of complete spinal cord injury on skeletal muscle cross-sectional area within the first 6 months of injury

In this study we examined the influence of complete spinal cord injury (SCI ) on affected skeletal muscle morphology within 6 months of SCI. Magnetic r esonance (MR) images of the leg and thigh were taken as soon as patients we re clinically stable, on average 6 weeks post injury, and 11 and 24 weeks a fter SCI to assess average muscle cross-sectional area (CSA). MR images wer e also taken from nine able-bodied controls at two time points separated fr om one another by 18 weeks. The controls showed no change in any variable o ver time. The patients showed differential atrophy (P = 0.0001) of the ankl e plantar or dorsi flexor muscles. The average CSA of m. gastrocnemius and m. soleus decreased by 24% and 12%, respectively (P = 0.0001). The m. tibia lis anterior CSA showed no change (P = 0.3644). As a result of this muscle- specific atrophy, the ratio of average CSA of m. gastrocnemius to m. soleus , m. gastrocnemius to m. tibialis anterior and m. soleus to m. tibialis ant erior declined (P = 0.0001). The average CSA of m, quadriceps femoris, the hamstring muscle group and the adductor muscle group decreased by 16%, 14% and 16%, respectively (P less than or equal to 0.0045). No differential atr ophy was observed among these thigh muscle groups, thus the ratio of their CSAs did not change (P = 0.6210). The average CSA of atrophied skeletal mus cle in the patients was 45-80% of that of age- and weight-matched able-bodi ed controls 24 weeks after injury. In conclusion, the results of this study early after SCI which differs among affected skeletal muscles. While the m echanism(s) responsible for loss of muscle size are not clear, it is sugges ted that the development of muscular imbalance as well as diminution of mus cle mass would compromise force potential early after SCI.