Diffusion Tensor Tractography In Prognostic Evaluation Of Patients With Cerebral Vascular Disease

Acute cerebral vascular disease is a common disease that harming the health of human severely, it is one of the three diseases mostly cause death. So it is very important to make a definite diagnosis, evaluate the state of the illness,judge the prognosis in the early state of the cerebral vascular disease. Diffusion tensor imaging (DTI) is a new magnetic resonance imaging technique developed in recent years, which can quantitatively analyse the diffusion motion of water molecules in tela on the three-demension and form the image by using the anisotropic character of the water molecules. Fiber tractography is the unique examination mainly used to evaluate the integrity of the cerebral white matter fiber tracts in vivo without any intrusion, which can clearly draw the courser and the spatial distribution of the main white matter fiber tracts and show the changes of the white matter fiber tracts which influenced by neurologic diseases. There is no domestic study about the dependablity between DTI and the prognosis of the cerebral vascular disease, so it need to be approached further. This study evaluated the degree of injury on the corticospinal tract (CST) of 18 patient with actue cerebral vascular disease using DTI and DTT examination, and graded the neurologic impairment of all the patients at the stage of onset, two-weeks after onset, a month after onset, two month after onset, to approach the dependablity between the injury of the corticospinal tract and the degree of the neurologic impairment, investigate the value of DTI examination used in the early stage of the cerebral vascular disease for judging the prognosis, provid basis for the clinical rehabilitation management.1. SubjectsFrom March 2006 to February 2007, 18 patients(14 men, 4 women, age range 30 to 70 years) with acute cerebral vascular disease in the first hospital of JiLin university were choosen as study cases, there are 16 patients with cerebral ischemic stroke, and 2 patients with hemorrhage. Inclusion standard: acute onset, diagnosed according to the diagnostic criteria of cerebral vascular disease, mostly having the hemiplegia as clinical manifestation. Exclusion standard: having obviously conscious disturbance and severe cognitive handicap.2. Process and parameter of the examination2.1 Every patients received magnetic resonance imaging(MRI) and diffusion tensor imaging(DTI);2.1.1 MRI was performed on a 1.5 T system (Siemens, Avanto) with a maximum gradient strength of 40 mT/m, and 200 T/m·s slew rate with a twelve-channel phased-array head coil.2.1.2 Standardized MRI examination: T1WI using SE sequence (TR/TE=3250/99ms), T2WI using TSE sequence (TR/TE =400/7.8ms),with transverse, coronal and sagittal orientation was applied. Slice thickness=2.3 mm, number of slice=15, and spacing of slice=1.8mm.2.1.3 DTI sequence: The imaging parameters used were as follows: TR/ TE = 3900/ 76 ms , field of view(FOV) = 230 mm×230 mm , matrix = 256×256, and a slice thickness of 3.6 mm. We acquired 33 contiguous slices parallel to the anterior commissure–posterior commissure line, b = 0 & 800 mm2 /s, with diffusion gradients applied in twelve non-collinear directions, eight averages, acquisition time: 2:40 minutes.2.1.3 Postprocessing: We evaluated fiber connectivity using a three-dimensional fiber reconstruction algorithm contained within the software package(Leonardo syngo 1852 ,Siemens). A seed region of interest was drawn on a two-dimensional FA color map at the mid-portion of the internal capsule and the cerebral peduncle to include the entire CST. The three-dimensional fiber tract was then superimposed on T2-weighted axial images in order to judge the injury degree of CST in the affected hemisphere.2.2 The muscle strength and NIHSS score of all the patients were judged at the stage of onset, two-weeks after onset, a month after onset, two month after onset.2.3 The injured CST expressed concordance was good, disfiguration and continous break, combining the muscle strength and NIHSS score at different stage, to judge the dependablity between the injury of the CST and the prognosis of the cerebral vascular disease.Results:①Reconstruction of bilateral CST, precentral gyrus to internal capsule and continued to pontine and medulla oblongata, and concordance was good in the uninjured side of the patients. The injured CST expressed concordance was good, disfiguration and continous break, because it was involved by stroke to different degree. There are 5 cases of grade 1(complete CST), 13 cases of grade 2(CST break).②Injured degree of CST in 16 patients with acute cerebral ischemic stroke was siginificantly associated with hemiplegia muscle strength and NIHSS score (p<0.05), the turnover of the NIHSS score at two month after onset having significant difference with the injury degree of the CST.③The muscle strength of the patient with hemorrhage having complete CST recovered quicker, and the NIHSS score at different stages were lower.④A total of 18 testes were involved in the result analysis. Injured degree of CST was siginificantly associated with hemiplegia muscle strength (at the atage of onset, a month after onset, two month after onset, p<0.05), Injured degree of CST was siginificantly associated with the NIHSS score (p<0.05), Injured degree of CST was siginificantly associated with turnover of the NIHSS score (p<0.05).Conclusion:①3D fiber tract maps can display the status of pyramidal tract more stereotacticly, and judge the injury degree of it at early stage of the cerebral vascular disease.②CST is injured to different degree in patients with acute cerebral infarction, and the degree of injury is associated with muscle strength and NIHSS score. The patients with complete CST would have lighter damage of the neuromotor function and better functional rehabilitation.③It is indicated that it can be used for prognosis of rehabilitative treatment in patients with hemorrhage.In a word, any reason cause the pathological changes of CST and motor functional region structure, effect its transmission function, will cause muscle weakness. The injure degree of CST has negative correlation with muscle strength, and positive correlation. Patients with lighter injury degree of CST will have better prognosis. Diffusion tensor tractography is the unique examination can evaluate the integrity of the cerebral white matter fiber tracts in three-dimensional without any intrusion, which can clearly show the changes of the white matter fiber tracts which influenced by neurologic diseases, and can provide major significance for judging clinical prognosis. Fiber tractography can provid useful information for clinical therapy, especially for the purposive treatment after neurofibra damage, have reference value for the study on functional evaluation regenerate neurofiber. In the future, fiber tractography will provid great space for the study of DTI, provide more important information for clinical rehabilitative treatment and judging prognosis.