Kikuchi Yoshito, Nakamura Toshiyasu, Takayama Shinichiro, Horiuchi Yukio, Toyama Yoshiaki
Department of Orthopaedic Surgery, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
Radiology. 2003 Dec;229(3):861-7. doi: 10.1148/radiol.2293020904. Epub 2003 Oct 23.
To describe the magnetic resonance (MR) imaging findings of denervation and reinnervation of skeletal muscles in rats.
The posterior tibial nerve was transected in 48 rats (nerve section group) and was repaired just after transection in another 48 rats (nerve repair group). At 2, 4, 6, and 8 weeks after surgery, changes in the area and signal intensity of the gastrocnemius muscle on T1- and T2-weighted MR images in vivo (four rats in each group) and T1s and T2s were analyzed in vitro in both groups (20 rats each) and compared with electromyographic findings. Water volume content and extracellular fluid space of the muscle in vitro were also examined in both groups (24 rats each). Four rats were used as controls for in vitro analysis.
At T2-weighted MR imaging, the muscle showed continuously high signal intensity in the nerve section group. In the nerve repair group, the signal intensity was high until 4 weeks, when it recovered. Increases in signal intensity on T2-weighted MR images and T2s were seen in the nerve section group throughout the study period. In the nerve repair group, increased signal intensity on T2-weighted MR images was noted at 2 and 4 weeks and significantly returned to normal at 6 weeks (P <.014), just after the detection of the M wave at electromyography. T2 increased at 2 weeks, then decreased significantly at 4 weeks (P =.012). Extracellular fluid space significantly increased in the nerve section group at all measurement times and in the nerve repair group at 2 and 4 weeks, then it decreased after 6 weeks (P <.003), which is parallel to the change in signal intensity on T2-weighted MR images, although there was little change in total water volume content in either group.
Changes in signal intensity on T2-weighted MR images that are related to denervation may result from an increase of extracellular fluid space. MR imaging clearly demonstrates that changes in rat skeletal muscle are reversed when the nerve heals and reinnervation proceeds.
描述大鼠骨骼肌去神经支配和再支配的磁共振（MR）成像表现。
将48只大鼠的胫后神经横断（神经切断组），另48只大鼠在神经横断后立即进行修复（神经修复组）。在术后2、4、6和8周，对体内T1加权和T2加权MR图像上腓肠肌的面积和信号强度变化（每组4只大鼠）进行分析，并对两组体外的T1s和T2s进行分析（每组20只大鼠），并与肌电图结果进行比较。还对两组体外的肌肉水含量和细胞外液间隙进行了检查（每组24只大鼠）。4只大鼠用作体外分析对照。
在T2加权MR成像中，神经切断组肌肉信号强度持续较高。在神经修复组中，信号强度在4周前一直较高，之后恢复正常。在整个研究期间，神经切断组T2加权MR图像和T2s上的信号强度均增加。在神经修复组中，T2加权MR图像上信号强度在2周和4周时增加，并在6周时显著恢复正常（P<.014），此时肌电图检测到M波。T2在2周时增加，然后在4周时显著下降（P =.012）。神经切断组在所有测量时间细胞外液间隙均显著增加，神经修复组在2周和4周时增加，但在6周后下降（P<.003），这与T2加权MR图像上信号强度的变化平行，尽管两组总水含量变化不大。
与去神经支配相关的T2加权MR图像信号强度变化可能是由于细胞外液间隙增加所致。MR成像清楚地表明，当神经愈合并进行再支配时，大鼠骨骼肌的变化会逆转。
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