大鼠正中神经修复后不同时段的电生理变化与神经再生的相关性分析

The characteristics of median nerve compound nerve action potential at different post injury and repair intervals and their correlation with nerve regeneration in rats

目的探讨大鼠正中神经切断缝合后的不同时段，其复合神经动作电位（CNAP）与形态学方面的特点及其相关性分析。方法在大鼠上臂正中神经中段切断缝合后的不同时间点（2、3、4．6、8和12周）进行CNAP检测，随后取正中神经组织进行形态学检查。结果术后第2周可以记录到CNAP。术后再生神经记录的CNAP幅度比对照组显著减低（P〈0．01），波幅下面积（Area）也显著低于对照组（P〈0．01），传导速度（cv）显著慢于对照组（P〈0．01）。术后2～6周的潜伏期（Lat）均比对照组明显延长（P〈0．05）；术后2。8周刺激强度，即阈强度（THI）和超大刺激强度（SSI）显著低于对照组。CNAP的第一峰波幅（FPA）、峰一峰波幅（PPA）、Area、CV变化趋势为随时间增加而逐渐增高，而其参数Lat、THI、SSI随时间增加而逐渐降低。神经修复后2周缝合口远端已有少量的新生轴突，随着再生时间延长，越来越多的再生轴突延伸至远端。远端记录的CNAP波幅与其有髓神经纤维计数之间有强的正相关（相关系数为0．953）。线性回归分析表明，存在线性关系。术后8周髓鞘趋向于成熟。结论CNAP是早期诊断和评价损伤神经再生程度的良好指标。正常正中神经的CNAP波幅可能与有髓神经纤维的计数呈线性关系。术后第8周，CNAP参数趋向于稳定，神经髓鞘渐趋向于成熟。

Objective To explore the characteristics of compound nerve action potential （CNAP） after rat median nerve transection and repair, and their correlation with neuromorphometry at various lime points. Methods The median nerve was transected and sutured at mid-arm level. At various time points from 2 to 12 weeks postoperatively, CNAP recording was performed and the median nerve was harvested for morphological examination. Results CNAP could be recorded at 2 weeks after nerve repair. The CNAP amplitude, the area below the curve （Area） and conduction velocity （CV） of regenerated nerve were significantly lower than those of control group （ P 〈 0.01 ）. From 2 weeks to 6 weeks postoperatively, CNAP latency （Lat） was obviously longer than normal （ P 〈 0.05）. From 2 weeks to 8 weeks postoperatively, CNAP stimulus intensity （ threshold intensity and the supramaximal stimulation intensity, THI and SSI） was significantly lower titan that of the control group （ P 〈0.01）. First peak amplitude （FPA）, peak-peak amplitude （PPA）, Area and CV of CNAP increased with time, while parameters such as I_at, THI and SSI decreased over time in regenerated median nerve. Regenerated axons could be seen at 2 weeks after nerve transection and repair. More and more regenerated axons were seen with the lapse of time. There was a strong positive correlation between CNAP amplitude and the number of myelinated nerve fibers, with a 0.953 correlation coefficient. Linear regression analysis revealed the existence of a linear relationship. The maturity of regenerated nerve at 8 weeks reflected by myelin sheath thickness was close to that of a normal median nerve. Conclusion CNAP recording is a valuable tool to evaluate the extent of early nerve regeneration after nerve suture repair. There might exist a linear relationship between CNAP amplitude of normal median nerve and the number of myelinated nerve fibers. CNAP parameters are inclined to stabilize and nerve myelin sheath maturation is close to normal 8 weeks postoperatively.