Mr Diffusion Tensor Imaging Experimental And Clinical Research On Compression Model Of Cervical Spinal Cord

PartⅠ: Establishment and physiopathology observation of cervical spinal cord compression injury model in goat for MRI researchObjective: To establish a stable, dominated and reduplicated compression model of cervical spinal cord, which was suitable for the research of MR imaging especially.Methods: Twelve goats weight 20 to 25kg were randomly divided into two groups: compression group and control group (n=6, respectively). A balloon catheter was inserted into the epidural space via the left intervertebral foramen between C2 and C3 for each goat. The balloon was advanced in the cranial direction and positioned at the level of intervertebral space between C2 and C3. The catheter was fixed to paraspinal soft tissue, then sewed up the cervical cut layer by layer, remained the end part of the catheter out of body and accomplished the compression model. After operation, intramuscularly injected penicillin 800,000 units each day, lasting for three days. In compression group, the balloon was inflated by slow injection 0.3ml of saline on the 10th day following operation and remained for 40 days. In control group, the balloon was not inflated, persistently observed for 50 days. Models were evaluated with MRI, modified Tarlov's motor function classification score and pathology. MRI was performed with a 3.0-T MRI system. Axial plane DTI was performed using single-shot echo planar imaging (EPI), a b-value of 500s/mm2, 6 diffusion gradient directions, 4 excitations and slice thickness of 3mm.Results: (1) Locomotor rating score: All goats could walk on the second day after operation, but ambulated rarely. Normal actions recovered after three days, locomotor rating score was 5. In compression group, the locomotor rating score was 3.50±0.40 on the first day of compression, lower than control group (t=36.40, P=0.005). Forty days after compression, muscle force of limbs recovered in some degree, the locomotor rating score was 4.20±0.50, but still lower than normal group(t=10.70, P=0.0017). (2) MR imaging: The balloon was located in the lateral-ventral side of the spinal cord. Before the balloon was inflated, the subarachnoid space at the level of C2-3 become narrow and the spinal cord was not compressed. In compression group, the balloon became oval and the spinal cord was moderately compressed after the balloon was inflated with 0.3ml of saline. All of the MRI image including DTI were clear without apparent distortion. At the beginning of compression, the ADC values decreased slightly and the FA values increased slightly at the compression site, then recovered to normality gradually. Forty days later, the ADC values became slightly higher and the FA values became slightly lower than normality. T1WI and T2WI at the compression site were normal. (3) physiopathology observation: In compression group, HE staining showed gently swelling and degeneration of axons and neurons at the compression site were observed. At the same time, auxiliary fibers disappeared partly, formation of cavities as well as infiltration of inflammatory cells and gliocyte proliferation could be seen. Toluidine blue staining showed Nissl bodies decreased in neurons, distribution was inhomogeneous. The disarrangement of myelin sheathes and degeneration of chondriosomes could be seen at transmission electron microscopy (TEM) examination. In control group, no abnormality could be seen under examination of light microscope and TEM.Conclusion: It is feasible to establish a goat cervical spinal cord compression injury model with balloon catheter via interspinal foramen. The degree, speed and duration of compression are under control. The evaluation of spinal cord function is easy with locomotor rating score. This model is free from laminectomy and the column keeps intact. By control injection volume and rate, the goat cervical spinal cord compression injury model is suitable for research on acute or gradual spinal cord compression injury, and is of great value for the research on physiopathology of spinal cord compression injury (SCCI) with MRI. PartⅡ: Experimental study of apoptosis and DTI functional evaluation after compressive spinal cord injury and decompressionObjective: To observation the apoptosis and the DTI change regularity after chronic compressive spinal cord injury (CCSCI) and decompression, to explore the relation between the physiopatholoy of neurofunctional recovery and imaging after decompression of CCSCI .Methods: Thirty-three goats weight 20—25kg were randomly divided into 3 groups: control group (Group A) and chronic compression spinal cord injury group (Group B) and decompression group (Group C). A balloon catheter was inserted into the epidural space at C2-3 level via intervertabral foramen for each goat, the balloon was advanced in the cranial direction and positioned at the level of intervertabral space between C2 and C3, to establish the animal model of chronic spinal cord compression. The locomotor rating score was applied to each group. Conventional MRI and DTI were performed. The cell apoptosis of spinal slice from the chronic compression injured spinal cord was examined by the terminal deoxynucleotidal transferase-mediated DUTP-biotin nick end labeling (TUNEL) reaction. The DTI and TUNEL were performed at 1,3,7,14 and 28 days post-compression and 1,3,7,14 and 28 days post-decompression.Results: (1) Locomotor rating score and MR imaging: In group A, the locomotor rating score was 5, and there was no abnormality on DTI and conventional MRI. In group B, the ADC and FA value kept unchanged before the volume of balloon reached 0.2ml. The ADC value began to increase slightly and the FA value began to decrease slight when the balloon reached 0.2ml, but the locomotor rating score remained unchanged. The ADC value began to drop and the FA value began to rise when the volume of balloon reached 0.4ml, the locomotor rating score dropped slightly. The ADC and FA value began to drop quickly when the volume of balloon reached 0.5ml or so, goats were severely paralyzed at the time. Myelorrhagia occurred in one goat at the 25th day after compression, there were no abnormality in others on conventional MRI. In the group C, locomotor rating score recovered slightly in the first seven days after decompression, the ADC and FA value increased slightly. Locomotor rating score , ADC and FA value recovered quickly in the period of the second seven days after decompression, some values eve n closed to normal. Fourteen days later, locomotor rating score , ADC and FA value recovered continually, but speed was slow. (2) physiopathology observation: In group A, nerve fibers were neatly arranged with no demyelination; the nucleus was big and round in neural soma with obvious nucleolus, Nissl body was abundant and accumulated around the nucleus. In group B, at 28 days post-compression,swelling and degeneration of axons and neurons, disarrangement of Nissl body, formation of cavities as well as infiltration of inflammatory cells could be seen under optical microscope. Each cord in white matter was injured, anterior cord, lateral cord adjacent to gray matter and the deep zone of posterior cord suffered from relative serious injury, which represented spongy degeneration and significant demyelination. Small vessels proliferated in servious demyelination area with increased vascular wall, hyaline degeneration and entourage infiltration by inflammatory calls. The number of neurons in the center and ventral horn of gray matter significantly reduced. Many neurons swelled with Nissl body dissolution and satellite phenomenon. In some slices, scarring could be seen in the necrosis zone with gliocyte proliferation; stress fissure appeared in the lateral cord of white matter. The severe the compression was, the more serious the spinal pathological injury was. In group C, at 28 days post-decompression, cavities formation and gliocyte proliferation in white matter became to lessen; swelling with Nissl body dissolution and satellite phenomenon in gray matter neurons also improved obviously. (3) TUNEL examination: In the process of CCSCI, cell death included two forms, necrosis and apoptosis, and apoptosis was predominant. Both necrosis and apoptosis caused injury to neurological function. Apoptosis cells largely located in ventral, lateral and dorsal column of the white matter, most of them were oligodendrocytes. Positive neuron occasionally emerged, most of them located in anterior gray horn. Apoptosis index was higher in the anterior two weeks post-compression. In two weeks post-decompression, apoptosis index decreased quickly, then kept at lower level.Conclusion: The ADC and FA value had high sensitivity in the detection of spinal cord chronic compression, they had the potential to be used in evaluating the progression of the histological changes following spinal cord compression injury quantitatively. Chronic compressive spinal cord injury could induced apoptosis, earlier decompression could inhabit apoptosis after CCSCI. The ADC and FA value and apoptosis correlated with the degree of clinical symptom.PartⅢ: Clinical value of MR diffusion tensor imaging in chronic cervical spondylotic myelopathyObjective:To evaluate the application of the diffusion tensor imaging (DTI) as a quantitative tool in chronic cervical spondylotic myelopathy with 3.0T MR.Methods: DTI examinations were performed in 31 consecutive healthy subjects and 64 patients with cervical spondylotic myelopathy (>2 years postinjury) by using SE-EPI sequence on the cervical spinal cord. The cervical cord was divided into 3 anatomic regions, the upper cervical cord included the region from the lower brain stem to the lower C2 vertebral body, the mid cervical cord included the region from the upper C3 vertebral body to the lower C5 vertebral body, and the lower cervical cord included the region from the upper C6 vertebral body to the lower C7 vertebral body. ADC, FA,λL andλT values of these examinee were analyzed with a software package of SAS V8.0.Results: (1) The control group: Neuromotor function score of the healthy subjects were normal. T1WI and T2WI images showed the cervical cords had not been compressed and showed uniform signals, no abnormal signals had been found. DTI images were clear without apparent distortion. On the ADC maps, normal cervical cords presented uniform dark blue color, CSF was red. On the FA maps, normal cervical cords presented uniform cardinal red color, CSF was bluish-green. For healthy people, averaged ADC values(F=1.00,P =0.3730),FA values(F=0.79,P=0.4557),λL values(F=0.79,P=0.4557)andλT values (F=0.18,P=0.8390)had no significant differences among 3 cervical cord regions. (2) The CSM group: T1WI and T2WI images showed the cervical cords were compressed due to canal stenosis, physiocurvature of the C-spines changed at difference degrees, intervertebral space became narrow, the posterior longitudinal ligament and ligamentum flavum formed reductus, osteophytic spur developed at margins of vertebral body edges, intervertebral discs hernia posteriorly due to ongoing dehydration and degeneration, 49 cases showed abnormal T2WI high signal intensity. ADC maps and FA maps showed CSF signal disappeared at the compression sites, signals of cervical cord were not uniform. Significant difference (P<0.0001) were observed in ADC(F=251.20),FA(F=47.54),λL(F=210.14),λT(F=104.39)between the upper and mid cord and also between the upper and lower cord levels in the patient group, had no significant difference between mid and lower cord levels. There were significant differences (P<0.0001)in ADC(t =20.82),FA(t =12.53),λL(t =6.00),λT(t =20.84)between control group and CSM group.Conclusion: ADC, FA,λL andλT values are sensitive factors for evaluating cervical spinal cord change in cervical spondylosis patient, DTI parameters are most marked at injury sites and reflect the severity of cord injury.