实验性腰椎管狭窄马尾神经动态负荷下血流量的变化

目的研究高频率刺激(high frequency stimulation,HFS)及压迫追加的动态负荷下双节段受压马尾神经血流量的变化,探讨神经源性间歇跛行的发病机制. 方法 SD大鼠30只,分成5组,每组6只.均行单纯L5椎板切除,检测血流量1小时后,将4个实验组制成L4及L6节段30%的双节段狭窄.施加静态压迫2小时后,实验1组不施加动态负荷(dynamic burden, DB);实验2组只施加HFS 6分钟;实验3组同时施加HFS和压迫追加6分钟;实验4组只行压迫追加6分钟;对照组为单纯L5椎板切除及HFS 6分钟.应用激光多普勒血流仪检测马尾神经血流量. 结果对照组马尾神经血流量在最初2小时无显著变化,施加HFS时显著升高至初始值的186.4%±31.5% (P<0.05).实验1组血流量为110.4%±7.5%(与初始值比较,P>0.05);实验2组血流量无显著变化111.6%±17.6%(与初始值比较,P>0.05);实验3组血流量降至初始值的65.3%±10.7%(P<0.05);实验4组血流量降至初始值的60.1%±9.2% (P<0.01),与实验3组无显著差异(P>0.05). 结论神经电活动增加时,马尾神经双节段压迫可造成其相对缺血;若压迫程度同时增加,马尾神经血流量显著降低,造成绝对缺血.

BLOOD FLOW CHANGES OF CAUDA EQUINA IN EXPERIMENTAL LUMBAR SPINAL CANAL STENOSIS UNDER DYNAMIC BURDEN

OBJECTIVE: To study the changes of blood flow of the already-compressed cauda equina under dynamic burden, high frequency stimulation (HFS) and increased additional compression, and to clarify the mechanism of neurogenic intermittent claudication. METHODS: Thirty SD rats were divided into 5 groups, 6 in each. All groups were operated with laminectomy of the fifth lumbar verfebra. One hour after the measurement of blood flow, in 4 experimental groups, the silicon sheets were inserted into the spinal canal of L4 and L6 to cause double level compression of cauda equina by 30%. Two hours after onset of compression, no dynamic burden was introduced to the subjects of the experimental group 1. Only HFS was introduced to the subjects of the experimental group 2 for 6 minutes. Both HFS and increased additional compression were introduced to the subjects of the experimental group 3 for 6 minutes. While only increased additional compression was introduced to the subjects of the experimental group 4 for 6 minutes. The subjects of control group only underwent laminectomy of the fifth lumbar vertebra and HFS 6 minutes. The blood flow of cauda equina was measured with laser Doppler flowmeter. RESULTS: In the first 2 hours, there was no significant change of cauda equina blood flow in the control group. During the time of HFS, the blood flow increased significantly to 186.4% +/- 31.5% of initial value (P < 0.05). In the experimental group 1, there was no blood flow change during the period of dynamic burden(110.4% +/- 7.5%, P > 0.05). After introduction of dynamic burden, there was no blood flow changes in the experimental group 2 (111.6% +/- 17.6%, P > 0.05). The blood flow in the experimental group 3 decreased to 65.3% +/- 10.7% of initial value (P < 0.05); and the blood flow in the experimental group 4 decreased to 60.1% +/- 9.2% of initial value (P < 0.01). There was no significant difference between the experimental groups 3 and 4 (P > 0.05). CONCLUSION: The results above show that during the period of increased impulse transmission, double level compression of cauda equina may limit the increase of blood flow, which may cause relative ischemia. If there is increased additional compression along with increased impulse transmission, the blood flow will decrease significantly, which will cause absolute ischemia.