Purpose: To detect the earlier changes of the skeletal muscle of rats after peripheral nerve injury by measuring the apparent diffusion coefficient (ADC) on diffusion MR spectroscopy. Materials and Methods: The posterior tibial nerve was transected in six rats (nerve transection group) and was only dissected in six rats (control group). At one, three, five, seven, 14, and 28 days after the surgery, both the T2 value and the ADC of gastrocnemius muscle were measured using a line-scan diffusion spectrum on a 1.5T clinical MR imager on both groups. Results: In the nerve transection group, the T2 ratio compared to the contralateral side increased gradually over four weeks after the transection, while the ADC ratio increased right after the surgery and began to decrease at five days. Four weeks after the transection, the ADC ratio returned to normal while the T2 ratio stayed at a high value. The control group indicated an almost constant T2 and ADC ratio during the experimental periods. Conclusion: The ADC of the skeletal muscle increased quickly after the transection of the dominant peripheral nerve and was detectable one day after the surgery. Diffusion MRI can be a useful tool for early detection of peripheral nerve injury instead of T2-weighted MRI or electromyography (EMG).
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