实验性脊髓损伤过程中体感诱发电位与运动诱发电位的变化及其意义

目的 观察实验性急性脊髓损伤过程中体感诱发电位(SEP)及经颅磁刺激运动诱发电位(TMS-MEP)的变化规律,探讨其应用价值.方法 将日本大耳兔32只随机分为4组,每组8只.A组为对照组,B、C、D组分别为轻、中、重度脊髓损伤组(脊髓压迫时间分别为5、15、30 min).于麻醉后,暴露脊髓后,伤后5、30 min、1、6、24 h和3、7 d分别检测各组动物SEP、MEP,对所得波形数据进行统计学分析.于伤后1、3、7 d采用后肢的Tarlov分级行运动功能评分.结果 刺激强度是影响TMS-MEP稳定性的一个比较重要的因素,100%刺激强度可获得稳定的波形.随着脊髓压迫时间的延长,SEP、MEP的潜伏期逐渐延长,波幅逐渐减小,波幅变化比潜伏期变化更加灵敏.在脊髓恢复过程中,潜伏期恢复早于波幅,SEP恢复早于MEP.结论 SEP与TMS-MEP对脊髓损伤十分敏感,二者结合能客观地反映脊髓损伤程度.

Changes of somatosensory and transcranial magnetic stimulation motor evoked potentials in experimental spinal cord injury

OBJECTIVE: To study the changes of somatosensory evoked potential (SEP) and transcranial magnetic simulation motor evoked potential (TMS-MEP) in experimental spinal cord injury (SCI). METHODS: Thirty-two rabbits were randomly divided into 4 equal groups. All rabbits were anesthetized for 90 min. A group (Group A) underwent only laminectomy of T12 without SCI, stimulation with different intensities was used to induce SEP and TMS-MEP to determine the most appropriate stimulation intensity. The EPs were recorded before and after the operation. The other 3 groups underwent laminectomy of T12 to expose the dura, and a spinal cord compressing apparatus weighing 40 g was put on the intact dura and dorsal surface of spinal cord underneath for 5, 15, and 30 min respectively (Groups B, C, and D). SEP and TMS-MEP were detected after anesthesia, after exposure of spinal cord, and 5 and 30 min, 1 and 6 h, and 1, 3, and 7 d. The latency and amplitude of each wave were measured. The data were analyzed by analysis of variance, t-test and linear correlation. Tarlov behavior score was used to assess the motor function before the operation and 1, 3, and 7 days after SCI. RESULTS: It was found that 100% intensity stimulus obtained stable and reliable MEP waves. Anesthetic did not influence the EPs. The amplitude of SEP began to decrease 5 min after SCI and the latency began to increase 30 min after SCI. And both the amplitude and latency, especially the former, of MEP began to significantly change 5 min after SCI. The latency levels of SEP and MEP increased and the amplitude decreased after compression time-dependently during a certain range of time (all P <0. 05). The latency of SEP recovered 1 d after SCI and the amplitude recovered 7 d after; and the latency of MEP recovered 3 d after SCI and the amplitude did not recover even 7 d after SCI. The Tarlov scores of all groups were all 5 before operation, and the Tarlov scores of Group C and D became 1 d after operation and then increased later, however, still lower than 5 even at day 7. CONCLUSION: SEP and TMS-MEP are very sensitive to SCI, in particular, the change of amplitude is more sensitive then the latency change and can more accurately reflect the degree of SCI. Combination of SEP and TMS-MEP objectively reflects the SCI degree. EP measurement, as a noninvasive technique, has great value in monitoring spinal cord function.