Establishment and evaluation of a new experimental animal model of chronic cervical compressive myelopathy

English Keywords:Chronic cervical compressive myelopathy  Sheep  Animal model  Balloon

English Abstract:

  【Abstract】　Objective：To explore a new experimental animal model of chronic cervical compressive myelopathy．Method: Nine small-tailed sheep were divided into three groups:control group（A），1-month group（B） and 3-month group（C）．The balloon was inserted into the C4/5 intervertebral space by anterior approach，and the syringe valve was fixed subcutaneously．Contrast agent was injected into the valve 0.1ml/week percutaneously．The sheep underent X-ray，CT and MRI under general anesthesia every four weeks．The Tarlov scores were assessed in each group．The spinal cord specimens at test level wｅｒｅ examined by optical microscope and transmission electron microscope at the end of experiment．ANOVA was applied to assess the difference of Tarlov scores among three groups, and the correlation of the parameters was analyzed by Pearson method．Result:The final radiological findings showed that the average spinal canal encroachment rate was 54.6% in group B and 67.6% in group C．Ｔｈｅｒｅ　ｗｅｒｅ　ｎｏ　Ｔａｒｌｏｖ　ｃｈａｎｇｅｓ　ａｆｔｅｒ　ａｎｄ　ｂｅｆｏｒｅ　ｐｅｒｃｕｔａｎｅｏｕｓｌｙ　ｉｎｊｅｃｔｅｄ．The final Tarlov score was 5（normal）in all the sheep of group A，5 in 2 sheep and 4 in 1 sheep of group B，3 in 2 sheep and 2 in 1 sheep in group C．The gross appearance of spinal cord in test level was normal in group A，flat in group B，and depressed in group C．The pathological examination showed neuronatrophy，increased gap around the neurons，reduction of Nissl body，mild demyelinated and vacuolar degeneration in group B，while more remarkably in group C．The ultrastructural pathology showed mild degeneration of neurons，slight expansion of rough endoplasmic reticulum，mitochondrial swelling，myelin sheath release，demyelination and vacuolar degeneration of some axons in group B，while more remarkably in group C，which presented with neuronal cell membrane breakdown，nuclear pyknosis，ribosomal depigmentation and disappearance of some axons．Conclusion:The postoperative behavior，radiological results and histological examination are in accordance with the character of chronic cervical compressive myelopathy， which can be used to establish a reliable and stable animal model of chronic cervical compressive myelopathy.