同侧颈_7神经根移位治疗臂丛上干根性撕脱伤患肢功能变化的实验研究

An experimental study on mechanism of functional compensation for file injured extremity with brachial plexus upper trunk avulsion repaired by ipsilateral C_7 nerve root transfer

目的研究臂丛上干根性撕脱伤再切取同侧颈,后不造成肢体功能进一步损害的代偿机制。方法60只SD大鼠随机等分为二组,上干根性撕脱+同侧颈_7神经根切断为实验组,单纯上干根性撕脱为对照组。术后3、6和12周每组取10只大鼠对颈_7神经根代表肌(背阔肌、肱三头肌、桡侧腕短伸肌和指总伸肌)作肌肉组织学、神经电生理与运动终板组织形态学的检测。结果术后3周实验组与对照组相比,四块颈_7代表肌的湿重显著减轻且肌细胞截面积缩小,复合肌肉动作电位(CMAP)的潜伏期显著延长并波幅明显下降,运动终板突触后膜面积明显减小,上述指标的二组差异均有统计学意义(P<0.05或P<0.01)。荧光显微镜观察显示实验组颈,代表肌的运动终板分布稀疏,电镜下可见形态不成熟的再生运动终板。伤后6周,实验组肱三头肌CMAP潜伏期及波幅的恢复率以及桡侧腕短伸肌与指总伸肌肌细胞截面积、CMAP潜伏期及波幅和突触后膜面积的恢复率与对照组相比,差异无统计学意义(P均>0.05)。实验组颈_7代表肌的运动终板数量已较3周时明显增多,超微形态亦趋于成熟。到12周,实验组各项检测指标的恢复率均已接近对照组(P均>0.05),其颈_7代表肌的运动终板分布密集且数量较多,超微结构接近成熟,形态与对照组基本一致。结论臂丛上干根性撕脱伤切取同侧颈,神经根后,下干神经纤维能通过末梢运动终板的再生对中干代表肌进行代偿性支配,故不会导致肢体功能的进一步损害。

Objective To investigate the mechanism of no further impairment of the injured upper limb function following ipsilateral C7 nerve root transection in brachial plexus upper trunk avulsion. Methods Sixty SD rats were divided into 2 groups. In the experimental group ipsilateral C7 root was transected after C5 - C6 root avulsion. In the control group only C5 - C6 root avulsion was created. Ten rats from each group were subject to electrophysiologic, histologic and histomorphometric examination of C7-innervated muscles including latissimus dorsi, triceps brachii , extensor carpi radialis brevis and extensor digiti communis muscles at post-operative 3, 6 and 12 weeks respectively. Results At 3 weeks post-operatively, significant differences were noted between the two groups. Compared to those of the control group, reduced muscle weight and muscle fibre area of the C7- innervated muscles, decreased amplitude and prolonged latent period of compound muscle action potential （CMAP） and diminished area of postsynaptic membranes were seen in the C7 root transection group （ P 〈 0.05 or P 〈 0.01）. Degraded distribution of motor end plates could be found under fluorescent microscope and immature structure of regenerative motor end plates under electron microscope in those muscles from the experimental group. At postoperative 6 weeks, there were no significant differences in recovery rate of amplitude and latent period of CMAP in triceps brachii muscle and recovery rate of muscle fibre area, amplitude and latent period of CMAP and area of postsynaptic membranes in extensor carpi radialis brevis and extensor digiti communis muscles between the experimental group and control group（ P〉 0.05）. The motor end plates were more than it had been at 3 weeks post-operatively. Furthermore, the ultrastructure of which also had a tendency to maturation. At 12 weeks after the operation, no significant differences were found in all parameters between the experimental and control groups（P〉0.05）. The motor end plates were populated and their ultrastrueture was close to a mature level similar to the control group. Conclusions Following ipsilateral C7 nerve root transection in brachial plexus upper trunk avulsion, neuraxons of the lower trunk could cempensatively dominate fibres of C7-innervated muscle by means of motor end plate regeneration, so that there was no further impairment in function of the affected extremity.