急性脊髓损伤时经颅磁刺激运动诱发电位监测的实验研究

Experimental research of myogenic motor evoked potentials to transcranial magnetic stimulation for spinal cord monitoring

目的 通过观察经颅磁刺激运动诱发电位 (TMS MEP)在急性脊髓损伤时的表现及其与功能预后的关系 ,探讨TMS MEP于临床手术时在脊髓运动功能监测中的应用。方法 32只家兔被随机分成 4组 ,对照组了解麻醉及手术对实验的影响 ,另 3组动物为脊髓损伤组 ,观察脊髓损伤后动物TMS MEP和运动功能的变化情况以及脊髓的病理学改变。结果 TMS MEP在脊髓损伤后有不同程度的恶化但并未完全消失的动物 ,大部分动物的运动功能能基本恢复正常 ;脊髓损伤后TMS MEP完全消失但其后 1h内能有不同程度恢复的动物 ,其运动功能可以大部保存 ;对于TMS MEP在脊髓损伤后完全消失而且后来一直未见有恢复迹象的动物 ,其运动功能的恢复大多较差。结论TMS MEP监测对脊髓的损伤非常敏感 ,伤时TMS MEP的表现与其后运动功能的恢复有着很好的相关性 。

Objective To evaluate the validity of intraoperative magnetic MEP(motor evoked potentials) monitoring in a spinal cord menaced surgery. Methods 32 rabbits were employed in weight drop spinal cord contusion model. After anesthetized with a combination of Ketamine and Droperidol the spinal cords were surgically exposed with the dura intact, and the contusion injuries were delivered except the rabbits in control group. The MEPs were recorded and the relationship between the variation of the MEPs and the residual locomotor capacity after spinal cord injury was analyzed. Results The 6 rabbits in mild spinal cord injury group experienced transient attenuation of their TMS MEPs, and the locomotor capacity remained intact (scores of 5) in almost all rabbits (5 of 6) when assessed 24 hours later; In the moderate spinal cord injury group the 8 rabbits lost their TMS MEP immediately after the weight drop contusion, but they regained them partly in 1 hour one after another and scored 4 or 5 in the assessment of muscle power next day except for one score of 2; 8 rabbits had their spinal cords impaired severely in the contusion procedure and lost their TMS MEP too but without recovery, their locomotor capacity outcomes were very poor, 5 of them had no response to transcranial magnetic stimulation next day, and in the other 3 rabbits we only found some polyphase waves with variant latency and lower amplitude which did not resemble common compound muscle action potential (CMAPs) evoked by TMS. Conclusions Myogenic TMS MEPs was very sensitive to the spinal cord injury and should be a valid technique for intraoperative monitoring, and a slight change of them, even if a transient lose, should be unnecessarily related to a severe movement disorder. The warning threshold for a given patient should depend on the malady itself.