| Cervical spinal cord injury is a disease with high disability rate and poor prognosis.The incidence of cervical spinal cord injury has a trend of increasing with continuous development of economy,transportation,construction industry,and aging population.Somatosensory evoked potentials(SEP)are clinically used to diagnose spinal cord diseases and intraoperative monitor in spinal cord operation.(1)Objective:A rat cervical chronic compression model was established for the cervical spondylotic myelopathy,and changes in behavioral test,SEP,and histopathological evaluations were analyzed with the duration of compression.Methods:The rat model of chronic cervical spinal cord compression was established at the C5 segment,and 72 SD female rats were randomly and equally divided into experimental and sham group.The behavioral test,SEP,and histopathological evaluations were performed at 1 week,2 weeks,4 weeks,8 weeks,12 weeks,and 24 weeks after compression.Results:BBB(Basso,Beattie&Bresnahan locomotor rating scale)scores decreased after surgery in experimental group and were minimized at 1 weeks.Since then,BBB scores were gradually restored and reaching a plateau after 4 weeks.The amplitudes of SEP decreased to the lowest at 1 week,and increased gradually,then plateaued after 4 weeks.Motoneurons in the anterior horn of the spinal cord were minimal at 2 weeks after compression,and the myelin staining intensity in the posterior column was less than that in the sham group at 1 week,2 weeks,12 weeks,24 weeks after compression,the myelin staining intensity in the anterior column was less than that in the sham group at 4 weeks,8 weeks,12 weeks,24 weeks correspondingly.The results showed the severe impairment of spinal cord in the compression model was at 1-2 weeks after surgery,and the spinal cord function gradually stabilized at 4-8 weeks,plateaued spontaneous recovery at 8-24 weeks.Conclusion:The result suggests that the optimal observation window of this model for studying the treatment is within 4 weeks after compression,the best observation window to study the neurorestoration is at 4-6 weeks,and the effect observation period of intervention methods is at 6-8 weeks.SEP can be used to evaluate the degree of spinal cord injury.(2)Objective:Decompression was performed on the rat chronic compression model,and changes in behavior test,SEP,and histopathological evaluations were analyzed before and after decompression at different compression times.Methods:45 female SD rats were randomly divided into sham group(n=5),compression group(n=5),decompression group which undergo decompression surgery at 1 week,2 weeks,3 weeks,and 4 weeks after compression(n=10 for each group).The behavioral test,SEP,and histopathological evaluation were performed at before and after decompression.Results:The BBB scores were elevated when the decompression was undergoing at 1 week after compression,however,BBB scores of 2 weeks after compression had no difference.The amplitudes of SEP were higher when the decompression surgery performed at 1 week after compression,in contrast,SEP of decompression at 2 weeks had lower amplitude than 1 week and sham group.Motoneurons in the anterior horn of the decompressed at 2 weeks decreased than 1 week group,the myelin staining intensity of the posterior column decreased concurrently.Conclusion:The results showed that decompression at 1 week after compression improved spinal cord function and spinal cord pathological injury,and decompression at 2 weeks were less effective than 1 week,suggesting that early decompression may promote recovery after spinal cord injury and improve spinal cord pathological injury.(3)Objective:To Compare the time-frequency components(TFCs)of SEP by time-frequency analysis in the cervical contusion,compression,and distraction injured rat models.Methods:The rat model of cervical spinal cord compression,contusion,and distraction injury was established at the C5 segment,and 10 rats in each group(include sham group)underwent median nerve SEP data collection post injury.The SEPs were analyzed by time-frequency analysis to extract the TFCs(time-frequency components).Results:The largest component of TFCs was taken as the main component,and others were defined as the sub-component.The main components of the contusion group had longer latency compared with the sham group and compression group,each group had no obvious difference in the frequency distribution,and the contusion group had lower energy than the sham group.Compared the PDF(probability density function)distributions of the sub-components of each group,three positions of highest probability density were S1,S2 and P3.In each group,S1,S2 and S3 had a similar position distribution.However,the contusion group had longer latency than the sham group at S1,the frequencies of the three injured groups were lower than the sham group at the same time.In the S2,the latencies of contusion and distraction group were longer than the sham group,while the frequency of each group was almost the same.In the S3 the compression and contusion group showed longer latencies compared with the sham group,but the frequency of three injured groups were higher than sham group.Conclusion:The results presented that the TFCs of the compression,contusion and distraction injury group had different characteristics.Above all,the result suggests that the optimal observation window of this model for studying the treatment is within 4 weeks after compression,the best observation window to study the neurorestoration is at 4-6 weeks,and the effect observation period of intervention methods is at 6-8 weeks.Afterward,early decompression can promote spinal cord recovery after injury,and SEP can evaluate the degree of cervical spinal cord injury.And finally,the time-frequency components of SEP have differential characteristics in the different cervical spinal cord injury patterns. |
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