| Background: Cerebral infarction is the most common type of stroke, the death rate of disability, whereas the upward trend in incidence, are seriously endangering the health of human life. Animal studies have shown that focal cerebral infarction can cause away from the primary tumor of the central nervous system (center never system, CNS) demyelination of nerve fibers, axonal degeneration and neuronal cell loss such as the secondary injury. Computed tomography (computed tomography , CT) and conventional magnetic resonance imaging (MRI) studies have shown that after supratentorial cerebral infarction, midbrain, pons and medulla oblongata, and even spinal cord infarction from a number of nerve fibers following onset damage; addition to cerebral infarction, the other primary focal brain damage such as cerebral hemorrhage, brain tumor, brain trauma, brain surgery, multiple sclerosis, can also cause secondary damage to nerve fibers; autopsy pathology also confirmed the existence of secondary damage. Therefore, the damage in CNS resulted from afocal cerebral infarct involved not only in the focal site but in regions far away from the initial lesion. The diffusion tensor imaging(DTI) is a new MRI technique based on diffusion-weighted imaging(DWI), which applied to study the molecular diffusion in biologic tissue. DTI can detect the cerebral damage by using to observe the diffusion of free water protons on the orientation of white matter fiber tracts. Contrast with conventional MRI, DTI can determine the diffusivity of every voxel and fully depict tissue diffusion characteristics. Therefore DTI takes the advantage in detecing the secondary impairments. Studies with DTI demonstrate that the secondary degeneration in pyramidal tract(PT) after a cerebral infarct advances with time course, and its process correlates with neurological deficit in acute stage and motor outcome same months late, focal thalamus infarction can also lead to the corresponding thalamic fibers secondary degeneration. Application of DTI-depth study of secondary degeneration of thalamic radiation fibers after thalamus infarction may help to further clarify the cause of focal cerebral mound structure and function of CNS damage mechanisms, and on recovery of neurological function in patients. However, the prospective reporte on the secondary degeneration of thalamic radiation fibers after thalamus infarction haven't seen in reports, its mechanism and the dynamic development process has not been clear, thalamus infarction secondary to nerve fiber degeneration will affect nerve function recovery, or how it affects the nerve function recovery of patients remains to be studied further. Therefore, the study secondary degeneration of thalamic radiation fibers after thalamus infarction both in theory and in clinical research have some guidance.Objective: Application of DTI technology forward-looking dynamic observation after focal cerebral lesions hill above the thalamic radiation fibers signal changes and the changes in DTI parameters, analysis of DTI parameters of patients and the relationship between neurological recovery, study after focal cerebral lesions at the top of hill thalamic fibers secondary radiation damage during the development of its clinical significance.Methods: continuous included from Jan 2008 to Jun 2009 at the First Affiliated Hospital of Guangxi Medical University, Department of Neurology, hospitalized cerebral infarction and in accordance with the following conditions for the experimental group, 17 patients:â‘ onset patients;â‘¡patients after MRI confirmed solitary unilateral thalamus infarction, in addition to infarction in other regions outside the region found no abnormal signals;â‘¢excluded patients with a history of cerebral infarction, cerebral hemorrhage such as the history of the central nervous system diseases. All the patients underwent conventional MRI, DTI and evaluation with the National Institutes of Health Stroke Scale (NIHSS),the Barthel Index (BI)and the Sensory disturbance rating (SDR) in the fiest week (W1), at the fourth week (W4) and at the end of the third month (W12) respectively. 17 age and gender matched volunteers underwent DTI one time as controls, Mean diffusivity (MD) and fractional anisotropy (FA)were measured at the region of interest (ROI): thalamic radiation semiovale levels. T test between the ipsilateral cerebrum and the control group. Repeat measure was established to reveal the time course of clinical scores and DTI quantitative date obtained at W1, W4 and W12. Spearman correlation analysis was used to assess the association between the FA value and the clinical scores.Results: In conventional MRI, there are invisible intensive signal changes in the thalamic radiation fibers of the ipsilateral cerebrum on W1 in all cases, hyperintense signal on T2-weight/FLAIR images of the ipsilateral semiovale which only 1 case on W4 and 2 cases on W12 can be seen respectively. However, on the map of FA, intensive signal derease in the PT at W1, W4 and W12,which contrast to the opposite site and controls. The FA values of lesion site, the ipsilateral proximal (centrum semiovale levels) and distal portion of PT (peduncle of cerebrum and pons) in patients significantly decreased at W1,W4 and W12 (P<0.01 respectively) .The MD of the centrum semiovale levels of thalamic radiation in patients was not significantly different at any time points (P>0.05 respectively ). The FA value of centrum semiovale levels of thalamic radiation did not correlated with all of NIHSS,BI and SDR (P>0.05).Conclusion: Focal thalamus infarction can cause secondary degeneration of thalamic radiation fibers, which can sometimes be found in conventional MRI, DTI not only demonstrate it with the map of FA, but it can identify and quantify the presence of secondary degeneration with the precise data of the FA value. we found that within 3 months of this secondary degeneration will be increased gradually with time, whether it may hinder the recovery of nerve function in patients needs further study. |
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