Foundmental And Clinical Studies On The Relationship Between The Increased Signal Intensity On MRI And Chronic Diseases Of Cervical Spinal Cord

Part one Correlation between increased signal intensity on MRI of cervical spinal cord and nerve cell apoptosisObjective: To explore the correlation between different MRI T2signal change and nerve cell apoptosis in chronic cervical spinal cord compressive disease.Methods: Thirty-two New Zealand white rabbits were randomly divided into two groups: control group (n=8), experimental group (n=24). Experimental group was operated on to set up the animal model of cervical spondylotic myelopathy. Six months after surgery, MRI examinations were performed, in which signal intensity ratio was calculated. HE staining, and Bcl-2, Bax immunohistochemical staining of spinal cord specimens were studied in all animals.Results: Increased signal on MRI T2images were observed in the experimental group, and the signal intensity ratio ranged from2.52to12.03. Few Bax and Bcl-2positive cells were observed in control group; in experimental group, Bax expressions increased, and the brown color darkened in cell plasms, Bcl-2expressions increased in cell nucleus. The statistical results showed that the correspondent optical density of Bax became larger and optical density of Bcl-2became smaller in white matter and gray matter with the increasing of MRI signal intensity ratio.Conclusion: MRI T2increased signal intensity was significantly related to cell apoptosis in chronic cervical spinal cord compression. With the increasing of signal intensity ratio, there were more cell apoptosis, more Bax expression, and fewer Bcl-2expression. Part two Significance of Increased S ignal Intensity on MRI in Prognosisafter Surgical InterventionObjective: Cervical spondylotic myelopathy (CSM) is a common spinal disease, the main pathological mechanism of which was chronic spinal cord compression that resulted in spinal cord degeneration and a series of clinical syndromes, which often occurs in people aged40-60years. Some patients may have history of trauma. Spinal cord can be compressed ventrally by the nucleus pulposus, vertebral osteophytes, hypertrophic ligamentum flavum or dorsally by the ossified posterior longitudinal ligament, which mainly leads to numbness and weakness of limbs, unsteady gait, and paresthesia, even paraplegia, bowel and bladder dysfunction in some severe cases. Some of the patients with CSM need surgical treatment, and the outcone is associated with many preoperative factors. Recently, magnetic resonance imaging (MRI) of the cervical spine, which not only reveals anatomic spinal cord compression, but also reflects the pathologic changes in the spinal cord, has become extremely valuable for this diagnosis, usually with satisfactory results. In addition, some scholars believe that several predictive parameters obtained by MRI, such as the compression rate of the spinal cord, the transverse area of the spinal cord, and signal intensity change of the spinal cord, may be related to the post-operative recovery of patients who undergo surgical treatments for CSM. However, there is controversy over the predictive effect of these imaging parameters, especially in regards to the signal intensity change of the spinal cord on T2-weighted MRI: the increased signal intensity (ISI) of the spinal cord on T2-weighted MRI and the decreased signal intensity on T1-weighted MRI are considered to predict a poor outcome. The controversy arises partly because the intensity change has been assessed only qualitatively, but not quantitatively. Several authors concluded that patients with focal area of high intensity change on T2-weighted MRI would have the same functional recovery as those without high intensity change. However, the number of compressed and operated levels of spinal cord was not mentioned clearly for patients with focal ISI in thses reports. As far as we know, there has not yet conclusive reports that depicted the significance of focal signal intensity changes on T2-weighted MRI in patients with single-level CSM. The purpose of the present study was to determine whether signal intensity changes demonstrated on T2-weighted MRI can help to predict the prognosis after anterior cervical decompression and fusion for patients with single-level CSM by means of measuring the ratio of T2/T1signal intensity.Methods: Between January2005and March2008,59patients (36men and23women) who underwent anterior cervical decompression and fusion for single-level CSM were included. Their mean age was53.8years (range,42-73years) at the time of surgery, and the mean duration of disease was21.3months (range,5-48months). All the patients were followed up for a minimum of2years. All patients underwent high-resolution MRI with a1.5-Tesla Siemens MAGNETOM Symphony (Siemens, Berlin, Germany) imager before surgery. Sagittal T1-weighted and T2-weighted images of the cervical cord were obtained using a spin echo sequence system for T1-weighted MRI and a fast spin echo sequence system for T2-weighted MRI. A cervical coil was used. The slice width was4mm, and the acquisition matrix was512×256. The sequence parameters for T1-weighted images was a repetition time (TR) of612ms and an echo time (TE) of13ms; and for T2-weighted images, a TR of2400ms and a TE of114ms was used. For patients with an ISI on T2-weighted MRI, the T2:T1ratio at the same spinal cord level, and over an area roughly equivalent to the ISI area on T2-weighted MRI, was calculated by computer. Patients were divided into3groups by hierarchical clustering analysis according to T2/T1ratio. Compression rate was measured at the target level of the spinal cord on T2-weighted axial image. All of the data were collected and reviewed by an independent observer. Two-time measurements of the data were performed and the mean value was used for analysis. Neurological status was assessed according to the Japan Orthopaedic Association (JOA) score, before and after surgery; and recovery rate, which was calculated.Results: Overall postoperative clinical outcome revealed significant improvement. The mean preoperative JOA score was10.1and was12.4at the final follow-up visit. No patient required additional cervical decompressive surgery for recurrent or residual symptoms. Of the52patients, no ISI was detected on the T2WIs in16patients (group1). The36patients with ISI were older, had a longer duration of disease, a worse postoperative JOA score, and a worse postoperative recovery rate than those without ISI. The T2/T1ratios for patients with ISI on T2WI ranged from1.18to2.77. These patients were subdivided into two groups, split by the median T2/T1ratio (1.77): there were18in group2(T2/T1ratio range:1.18-1.74) and18in group3(T2/T1ratio range:1.79-2.77). The analysis of variance showed significant differences in the preoperative (P<0.001) and preoperative JOA scores (P<0.001) and the recovery rate (P<0.001) among three different groups. In addition, the Student-Newman-Keuls (SNK) test for the preoperative JOA score showed significant differences between groups1and2(P<0.05), groups1and3(P<0.05), and groups2and3(P<0.05). Significant differences for the final JOA score were noted between groups1and2(P<0.05), groups1and3(P<0.05), and groups2and3(P<0.05). When comparing the T2/T1ratio and recovery rates for the three different groups, significant differences were found between groups1and2(P<0.05), groups1and3(P<0.05), and groups2and3(P<0.05).Conclusion: Patients with ISI and higher T2/T1ratio tend to have relatively severe preoperative state of illness and poor prognosis after surgical intervention. Spinal cord signal intensity change on T2-weighted MRI might be a predictor of a poor outcome in terms of functional recovery rate in patients underwent operations for multi-level CSM.Part three Prognosis significance of focal signal intensity change on MRI after anterior decompression for single-level cervical spondylotic myelopathyObjective: Cervical spondylotic myelopathy (CSM) is a common spinal disease, the main pathological mechanism of which was chronic spinal cord compression that resulted in spinal cord degeneration and a series of clinical syndromes, which often occurs in people aged40-60years. Some patients may have history of trauma. Spinal cord can be compressed ventrally by the nucleus pulposus, vertebral osteophytes, hypertrophic ligamentum flavum or dorsally by the ossified posterior longitudinal ligament, which mainly leads to numbness and weakness of limbs, unsteady gait, and paresthesia, even paraplegia, bowel and bladder dysfunction in some severe cases. Some of the patients with CSM need surgical treatment, and the outcone is associated with many preoperative factors. Magnetic resonance imaging (MRI) can not only show the degree of compression of the spinal cord but also reflect the changes within the spinal cord in detail, for instance, increased signal intensity (ISI) might reflect myelomalacia or gliosis due to long-term compression of the spinal cord. The significance of ISI for prognosis remains controversial, though many studies had investigated the association between ISI and surgical outcome. Some authors reported that ISI is a predictor of poor prognosis after surgery. However, others found no correlation between surgical outcome and intramedullary ISI. Several authors concluded that patients with focal area of high intensity change on T2-weighted MRI would have the same functional recovery as those without high intensity change. However, the number of compressed and operated levels of spinal cord was not mentioned clearly for patients with focal ISI in thses reports. As far as we know, there has not yet conclusive reports that depicted the significance of focal signal intensity changes on T2-weighted MRI in patients with single-level CSM. The purpose of the present study was to determine whether signal intensity changes demonstrated on T2-weighted MRI can help to predict the prognosis after ACDF for patients with single-level CSM by means of measuring the ratio of T2/T1signal intensity.Methods: The participants in this study were59patients who underwent anterior cervical decompression and fusion for single-level CSM. There were36men and24women (mean age at the surgery,53.8years; range,42-73years). The symptom duration of these patients ranged from5to48months; with a mean symptom duration of21.3months. All patients underwent high-resolution MRI with a1.5-Tesla Siemens MAGNETOM Symphony (Siemens, Berlin, Germany) imager before surgery. Sagittal T1-weighted and T2-weighted images of the cervical cord were obtained using a spin echo sequence system for T1-weighted MRI and a fast spin echo sequence system for T2-weighted MRI. A cervical coil was used. The slice width was4mm, and the acquisition matrix was512×256. The sequence parameters for T1-weighted images was a repetition time (TR) of612ms and an echo time (TE) of13ms; and for T2-weighted images, a TR of2400ms and a TE of114ms was used. The T2:T1ratio at the same spinal cord level, and over an area roughly equivalent to the ISI area on T2-weighted MRI, was calculated by computer. Patients with ISI were subdivided into3groups by hierarchical clustering analysis according to T2/T1ratio. Neurological status was assessed according to the Japan Orthopaedic Association (JOA) score, before and after surgery; and recovery rate, which was calculated.Results: Anterior decompression was performed at C3-C415in patients, C4-C5in22patients, C5-C6in13patients and C6-C7in9patients. Fusion was achieved with tricortical iliac crest graft in21patients, titanium cage filled with bone in38patients. Overall postoperative clinical outcome showed significant improvement. The mean preoperative JOA score was9.6, and12.7at the final follow-up visit, it had improved to a mean score of3.1. The mean recovery rate was45.7%at the final follow-up visit. The range of T2/T1ratio of59patients was from1.26to2.85. Twenty patients were divided into group1(ratio range,1.26-1.67),16into group2(ratio range,1.7-2.18) and23into group3(ratio range,2.25-2.85). Analysis of variance showed significant difference in age at surgery (P<0.001), duration of disease (P<0.001), recovery rate (P=0.036), pre (P<0.001) and preoperative JOA score (P<0.001) among three different groups, but there was no significant difference in compression rate (P=0.102). Student-Newman-Keuls (SNK) test of age showed significant difference between groups1and2(P<0.05), groups1and3(P<0.05), and groups2and3(P<0.05). SNK test of duration of disease showed significant difference between groups1and2(P<0.05), groups1and3(P<0.05), and groups2and3(P<0.05). In addition, SNK test of pre and postoperative JOA score showed significant difference between groups1and3(P<0.05), groups1and3(P<0.05), and groups2and3(P<0.05). No significant difference in recovery rate was observed between groups1and2(P=0.199), and between Groups2and3(P=0.227), though there was significant difference between Groups1and3(P<0.05). Spearman’s rank correlation showed that T2/T1ratio was correlated with age at surgery (rs=0.577, P<0.001), duration of disease (rs=0.652, P<0.001), compression rate (rs=0.416, P=0.001), pre (rs=-0.759, P<0.001) and postoperative JOA score (rs=-0.732, P<0.001), and recovery rate (rs=-0.564, P<0.001). Stepwise regression analysis showed that the best combination of surgical outcome predictors included preoperative JOA score and duration of disease..Conclusion: Patients with higher T2/T1ratio tend to have relatively poor prognosis after surgical intervention. Focal spinal cord signal intensity change on T2-weighted MRI might be a predictor of a poor outcome in terms of functional recovery rate in patients underwent operations for single-level CSM.