慢性压迫性脊髓症研究平台的建立及体感诱发电位功能评价的机制

目的 建立新型大鼠脊髓慢性压迫模型,进一步探讨体感诱发电位(somatosensory evoked potential,SEP)对慢性压迫性脊髓症的诊断价值及其对应的病理生理改变.方法 15只大鼠经后路手术于颈椎管内植入吸水性聚氨酯胶片,植入体内会逐渐吸水胀大,形成对脊髓的慢性持续压迫.术后6个月,对慢性压迫脊髓进行SEP、影像学、组织学和组织化学检测.结果 15只造模大鼠脊髓均出现侧后方明显压迫性形态学改变,微焦点计算机断层扫描显示脊髓灰质和白质扭曲变形.9只表现为潜伏期延长和(或)波幅F降等SEP异常,SEP反应分为Ⅰ型6只、Ⅱa型5只、Ⅱ b型2只、Ⅲ型2只.正常和异常SEP的脊髓压迫率差异无统计学意义(P>0.05).SEP反应异常的大鼠与反应正常者脊髓的组织学、组织化学比较,脊髓后索髓鞘染色显著减少(Ⅱ a:106±12,Ⅰ:121±8,P=0.038),脊髓后索的对比剂密度差异有统计学意义(Ⅱ a:95±5,Ⅰ:87±6,P=0.042),而且后角内神经元也明显较少Ⅱ a:(25±8)/mm~2,Ⅰ:(29± 6)/mm~2 P>0.05];Ⅱ b型和Ⅲ型不仅脊髓后索髓鞘着色减少,灰质后角神经元密度只有(16±5)/mm~2和(14±5)/mm~2;均出现基质海绵样变和静脉扩张.结论 在慢性压迫性脊髓症发展过程中,SEP出现异常迟于形态学改变,但是反映了脊髓后索和后角神经元损伤的严重程度.为深入研究脊髓型颈椎病的病理生理机制和疗效评估提供了良好的动物模型.

The establishment of the experimental chronic compressive myelopathy and the mechanism of somatosensory-evoked potential's evaluation

Objective To explore the pathophysiological changes behind somatosensory evoked po-tential (SEP) defect and its diagnostic value in an established model of spinal cord chronic compression. Methods Total 15 rats were operated with implantation of a water-absorbing polymer sheet in cervical spinal canal, which expanded gradually to induce chronic compression to the spinal cord. At 6 months after surgery, SEP, radioiogical and pathohistological/istochemistry evaluations were done. Results Spinal cord in 15 rats showed significant morphological compressed deformity after chronic compression. It was also characterized by higher contrast intensity and distortion of gray matter and whiter matter under micro-CT e-valuations. SEP revealed that nine rats had prolonged latency and/or decreased amplitude. Based on their different SEP response, they were categorized into: type Ⅰ (n=6), type Ⅱa (n=5), type Ⅱb (n=2), type Ⅲ (n=2), and type Ⅳ (n=0). Compression ratio was not different between normal and abnormal SEP responses in the rats. Compared with the rats with normal SEP responses, the spinal cord of rats with normal SEP responses showed less myelin staining in white matter(Ⅱa: 106±12 vs.Ⅰ: 121±8; P=0.038), less contrast medium density in posterior dorsal column (Ⅱa: 95±5 vs. Ⅰ: 87±6; P=0.042), lower neuron density and cavitation in gray mat-terⅡa: (25±8)/mm~2 vs. Ⅰ: (29±6)/mm~2, P>0.05]. Less myelin staining in posterior column whiter matter could be seen in type Ⅱb and Ⅲ. Neuron density in posterior horn of gray matter were (16±5)/mm~2 and (14± 5)/mm~2 respectively. Histological cystic cavitations and sinusoidal dilation of veins were noted in spinal cord with significant distortion after compression. Conclusion SEP responses reflected the severity of spinal cord posterior tract and horn damage in chronic compressive injuries after gross appearance changes.