Experimental Study Of Paraspinal Muscle Denervation On Scoliosis Associated With Syringomyelia In The Early Stage

Objective:In this experimental study, we wanted to explore the relationship between the formation of scoliosis and paraspinal muscles denervated, on the rabbit model of scoliosis associated with communicative syringomyelia (SM) which was induced by cisterna magna puncture and Kaolin injection, and provide a basis for the mechanism of formation of scoliosis which associated with syringomyelia, in the early formation of scoliosis.Methods:This study was divided into two parts.Part I:To establish rabbit animal model of communicative syringomyelia associated with scoliosis which induced by cisterna magna puncture and Kaolin injection.The animals used for the experiment were40young rabbits, age about3months and weight1.75-2.25kg. They were divided into four groups randomly. Group A, which was16rabbits used as cisterna magna puncture and Kaolin injection; Group B, which was8rabbits for cisterna magna puncture and saline injection; Group C, which was8rabbits for cisterna magna puncture just only, and Group D, which was8rabbits used as blank control. The animals in every group were numbered randomly. Group A, We did cisterna magna puncture with lml injector, drawn out0.6ml cerebrospinal fluid first and then injected the same amount of sterile25%Kaolin suspension; Group B,We did cisterna magna puncture with1ml injector, drawn out0.6ml cerebrospinal fluid first and then injected the same amount of sterile saline; Group C, We did cisterna magna puncture just only, neither drawn out the cerebrospinal fluid not injected any substance; Group D, not doing any processing.After the animal model was established, we choosed1,3,6,9,12weekends for the test time points, took spinal full-length anteroposterior X-ray films, and cervical spine magnetic resonance imaging(MRI) scan, syringomyelia and the occurrence of scoliosis were recorded at each time point in experimental animals. Part II:Spinal cord conduction and paraspinal muscle denervation study between communicative syringomyelia and syringomyelia associated with scoliosis.In the12th weekend, the animals were divided into two groups which according to the results by imaging confirmed whether syringomyelia associated with scoliosis in groupA experimental animals. Group Al: There were5rabbits which were syringomyelia associated with scoliosis; Group A2:which were5rabbits just with syringomyelia; Group D':The5rabbits used as control which were choose from group D randomly. Each experimental animal was tested the rabbit bilateral posterior tibial nerve P40somatosensory evoked potential (SSEP) and measured by the latency and peak amplitude. To do the construction among each groups and do bilateral own companions in scoliosis group by bilateral average of the latency and peak amplitudea, at last make statistical anlysis. After the animal death, the incidence of syringomyelia has once again proven by the cervical spinal histological detection with HE stain; Next, we observed the lesions of bilateral paraspinal muscle tissue with HE stain, and calculated paraspinal muscles axon terminals innervation ratio (TIR) of paraspinal muscles with motor endplate nerve silver stain. Through the way of Coers, got the TIR average with each group; and observed the paraspinal muscles ultrastructural changes in scanning electron microscope.Results:1. General situation result:All of the animals were no death in12weeks of the observational process. Group A:general animals showed varying degrees of listlessness and less eating, but no limb movement disorder,unsteady gait and persistent weight loss during1-7days after operation. Group B:The animals also had little mental apathetic performance, but all the animals returned to normal within one week. The group C and group D not any anomalies are observed.2. The imaging results:Group A:SM was observed after3weeks operation by MRI imaging, and there were1,2,4,3animals be observed on the3th6th9th12th weekend respectively. The incidence of SM was62.5%on the12th weekend. When the6th weekend after operation, scoliosis was detected in the animal associated with SM by X-ray. Scoliosis was observed on the6th,9th,12th weekend were1,2,2animals respectively, and the incidence of scoliosis was31.3%on the12th weekend, incidence of SM associated with scoliosis was50%.The shape and angle of scoliosis were be worse over time. The other groups showed no occurrence of SM and scoliosis.3. Electrophysiology: There was no significant statistical difference in the degree of latency and peak amplitude among these three groups by examination of P40cortical SSEP. There was no significant statistical difference in the degree of latency and peak amplitude between the convex and concave side in scoliosis group too.4. The spinal cord and paraspinal muscle histology:(1) There are different degrees expansion on the central canal of cervical spinal cord, were be found, especially the segments of C2-C5, in Al and A2groups with HE staining. Coincidence rate of pathologic examination and MRI was100%.(2) Paraspinal muscles and nerve endings by light microscopy: There many changes were be observed in the group Al, included that small social muscle atrophy,atrophic muscle fibe,angular cells and subcellular structural disorder, especially the changes of terminal branch increasing in axon. The similar changes were not be observed in group A2and group D'. TIR value: the blank control group D':1.07±0.15;simple syringoyelia group A2:1.04±0.18; Syringoyelia associated with scoliosis group Al:1.32±0.05.(3) Paraspinal electromyography: The changes were be detected in paraspinal muscles group Al,included that dissolution of under the sarcolemma and between myofibrils myofilament,the intermittent sarcolemma damage and widespread expansion of sarcoplasmic reticulum,swelling of mitochondria and the crest is unclear or formation of myelin-like structures. The similar changes were not found between the simple syringomyelia group and blank control group.Conclusion:(1) Animal model of cervical syringomyelia can be induced by the cisterna magna puncture and kaolin injection, this method is simple,mature verification method and high success rate.(2) Scoliosis may be occurred in the process of syringomyelia formation, but the relationship between the two just need further more study. (3) There was no obvious abnormalities be found on spinal proprioceptive sensibility conductive function in the early stage of syringoyelia associated with scoliosis.(4) In the early stage of syringoyelia associated with scoliosis, bilateral paraspinal muscle denervation may be the middle part or the secondary change rather than initiating factor.