BACKGROUND: Magnetic resonance diffusion tensor imaging (MRDTI) may non-wounded detect damage of fiber in white matter and becomes an effectively way to evaluate upper motor neuron(UMN) impairments.OBJECTIVE: To investigate the clinical significance of MRDTI on amyotrophic lateral selerosis(ALS).DESIGN: Case contrast observation.SETTING: Department of Neurology, Renmin Hospital of Wuhan University.PARTICIPANTS: Twenty ALS patients were selected from Department of Neurology, Renmin Hospital of Wuhan University from April to December 2005. There were 11 males and 9 females, and their ages ranged from 33 to 73 years with the mean age of (51±10) years. All subjects met the diagnostic criteria of ALS set by World Neurology League.Other 15 healthy subjects were collected as control group. There were 8 males and 7 females, and their ages ranged from 31 to 73 years with mean age of (50±11) years. All subjects provided the confirm consent.METHODS: Based on level of upper and lower motor neuron impairments, ALS patients were divided into UMN impairment group (n =16) and lower motor neuron group (n =4). Functional scores of ALS, illness developing velocity and pyramidal sign scores were performed, respectively. All subjects were scanned with DTI at axial view. Regions of interest [subcortical white matter of precentral gyrul and postcentral gyrul (Pre-CG/Post-CG), centrum semiovale and frontal white matter (CS/FWM), peripheral lateral cerebral ventricle, posterior limb of internal capsule (PIC), cerebral peduncle (CP), genu corpus callosum and splenium corpus callosum (GCC/SCC) and dorsal thalamus (DT)] were selected to measure fractional anisotropy (FA) and apparent diffusion coefficient(ADC).MAIN OUTCOME MEASURES: Correlations among FA, ADC, functional score of ALS, illness developing velocity and pyramidal sign scores.RESULTS: Twenty patients and 15 subjects in the control group were involved in the final analysis. ① FA was reduced and ADC increased in the posterior limb of the internal capsule in patients with UMN signs compared to healthy volunteers (t =3.452, 2.670; P ＜ 0.01, 0.05). Nonparametric tests revealed that there was a trend toward reduced FA in the posterior limb of the internal capsule in B group compared to controls (U =11, P =0.057). ② In UMN impairment group, FA in the posterior limb of the internal capsule was positively correlated with the ALS rating scale (r =0.577, P ＜0.05) and negatively correlated with pyramidalsign scores (r = -0.789, P ＜ 0.01 ),CONCLUSION : The impairment of pyramidal tracts can be noninvasively evaluated by diffusion tensor MR in vivo, thus providing useful information in diagnosing and further understanding MND.