The Quantitative Measurements Of Magnetic Resornance Diffusion Tensor Imaging For Upper Motor Neuron Damage Of Patients With Amyotrophic Lateral Sclerosis

PURPOSE: To investigate the quantitative evaluation of diffusion tensor MRI forupper motor neuron damage in ALS.METHODS: According to World Federation of Neurology Research Group's ALSdiagnostic standard, We choosed twenty-one people as patient group, and dividedthem into A group (bulbar onset) and B group (extremity onset). Twenty healthy age-and sex- matched volunteers were served as control group. All subjects underwent aDTI sequence. DTI was performed using a single shot SE-EPI with 25 non-collineardiffusion gradient directions (b=1000s/mm~2) on a 1.5-T MR system. Fractionalanisotropy(FA)and mean diffusivity(MD)were quantitatively measured in 11 regionsin bilateral pyramidal and non-pyramidal tract regions, including the corticalsubstance of precentral gyrul, the subcortical white matter of precentral gyrul,centrum semiovale, periventricular white matter, genu corpus callosum, spleniumcorpus callosum, dorsal thalamus, posterior limb of internal capsule, cerebralpeduncle and medulla pyramid. All subjects underwent TMS-MEP examination,threshold value and central motor conduction time (CMCT) of motor cortex whichdominated upper and lower limb were quantitatively measured. All subjectsunderwent ALS function rating scale and upper motor neuron dysfunction scale.RESULTS: 1. In ROI of pyramidal tract regions, FA of the cortical substance ofprecentral gyrul (u=-4.002, P＜0.01),the subcortical white matter of precentralgyrul (u=-3.974, P＜0.01), centrum semiovale (u=-3.580, P＜0.01), periventricularwhite matter (u=-3.581, P＜0.01), posterior limb of internal capsule (u=-3.974,P＜0.01), cerebral peduncle (u=-3.580, P＜0.01) and medulla pyramid (u=-2.402,P＜0.05) decreased significantly and MD of the subcortical white matter of precentralgyrul (u=-2.431, P＜0.05), posterior limb of intemal capsule (u=-2.168, P＜0.05)increased in patient group, compared with those in control group. In ROI ofnon-pyramidal tract regions, FA of splenium corpus callosum (u=-2.004, P＜0.05) and dorsal thalamus (u=-3.580, P＜0.01) decreased in patient group, compared withthose in control group.2. FA of the cortical substance of precentral gyrul, the subcortical white matter ofprecentral gyrul, centrum semiovale, periventricular white matter, posterior limb ofinternal capsule, cerebral peduncle, medulla pyramid and dorsal thalamus decreased,MD of the subcortical white matter of precentral gyrul increased in A and B group,compared with those in control group. The differences of FA and MD of each ROIbetween A and B group were no statistic meaning, but FA of the cortical substance ofprecentral gyrul, the subcortical white matter of precentral gyrul, periventricular whitematter, posterior limb of internal capsule and dorsal thalamus showed decreasedtendency in A group, compared with those in B group.3. The differences of upper limb motor cortex threshold value (u=-4.560, P＜0.01),CMCT (u=-4.639, P＜0.01) and lower limb motor cortex threshold value (u=-4.213, P＜0.01),CMCT(u=-4.712, P＜0.01)between patient group and control grouphad statistic meaning. The threshold value of upper and lower limb motor cortexincreased significantly, and CMCT of upper and lower limb motor cortex prolongedsignificantly in patient group, compared with those in control group.4. FA of posterior limb of internal capsule had positive correlation with ALS functionrating scale (r_s=0.701, P=0.024), and had negative correlation with the score ofupper motor neuron dysfunction (r_s=-0.644, P=0.044), and had no correlationwith age, illness duration and disease progression rate in patient group. MD ofposterior limb of internal capsule had no correlation with all above clinical variables.5. FA of posterior limb of internal capsule had negative correlation with upper limbmotor cortex threshold value (rs=-0.736, P=0.015), CMCT (r_s=-0.695, P=0.026)and lower limb motor cortex threshold value(r_s=-0.754 P=0.012), CMCT(r_s=-0.729, P=0.017) in patient group. There was no correlation of MD with allabove variables.CONCLUSIONS: 1. FA and MD of pyramidal tract in patient group had significantchange, compared those in control group. They can evaluate the pathologic change ofpyramidal tract of ALS patients objectively and quantitatively, and provide valuableinformation for the diagnosis of ALS. Further more, FA is more sensitive than MD,and posterior limb of internal capsule may be the optimal area for the assessment ofpyramidal tract damage. 2. The degeneration of neuron of ALS is not limited in pyramidal tract, other parts ofbrain such as splenium corpus callosum and dorsal thalamus are also affected. Itmeans that ALS may be a kind of multisystem degeneration disease.3. FA of the cortical substance of precentral gyrul, the subcortical white matter ofprecentral gyrul, periventricular white matter, posterior limb of internal capsule anddorsal thalamus showed decreased tendency in bulbar onset group, compared withthose in limb onset group.It means that the damage of upper motor neuron of patientwith bulbar onset is worse than patien with limb onset, or the pathologic change ofthis type patient is different with other types. Because the sample of our research issmall, there still need to increase the amount of sample to carry out futher research.In a word, DTI can evaluate the degeneration of pyramidal tract, and afford valuableinformation for the diagnostic of ALS.