MRI及MR扩散张量成像对肌萎缩侧索硬化症的初步评价

目的　描述肌萎缩侧索硬化症 (ALS)的脑部MR影像学表现特点 ,探讨常规MR成像及MR扩散张量成像 (DTI)部分各向异性 (FA)值在本病诊断中的价值。方法　对 14例临床确诊的ALS患者和 12例正常人行MR扫描 ,其中 2例患者行增强扫描。对 10例患者及 12例正常人行DTI横轴面和冠状面扫描 ,使用自旋回波 回波平面成像 (SE EPI)序列 ,b值为 10 0 0s/mm2 ,扩散敏感梯度方向为 2 5。为定量评价锥体束 ,在内囊后肢和中脑大脑脚水平测量双侧锥体束的FA值并做统计学处理。结果　 6例患者双侧内囊后肢呈局限性T1WI略低信号及T2 WI高信号 (高于皮层信号 ) ,冠状面T2 WI可明确显示内囊后肢至大脑脚纵向连续的带状高信号影 ,符合锥体束走行 ;8例患者双侧内囊后肢呈局限性T1WI略低信号及T2 WI略高信号 (与皮层信号相等 )。 2例行增强扫描者均未见异常对比增强。 12例正常人双侧内囊后肢均呈局限性T1WI略低信号及T2 WI略高信号 (与皮层信号相等 )。病变组FA值在内囊后肢水平和中脑大脑脚水平均明显低于对照组FA值 (F =7.38,P <0 .0 1;F =7.31,P =0 .0 1)。结论　常规MR成像诊断ALS时须结合临床资料。ALS患者锥体束区域FA值的下降提示存在神经元变性及继发性脱髓鞘 ,DTI可以在活体无创性地对锥体束及其潜在病变进行检测和评价

Preliminary assessment of amyotrophic lateral sclerosis by using MRI and MR diffusion tensor imaging

Objective To describe the characteristic MR findings in the brain in patients with amyotrophic lateral sclerosis (ALS), and to assess the diagnostic value of conventional MR imaging and fractional anisotropy (FA) of diffusion tensor imaging (DTI). Methods Conventional MR imaging was performed in 14 clinically proved ALS patients and 12 age-matched normal controls. Contrast enhanced MR images were acquired in 2 patients. Axial and coronal DTI scans were performed in 10 patients and 12 normal controls with SE-EPI sequence. The b value was 1 000 s/mm 2, the number of diffusion sensitive gradient direction was 25. For quantitative assessment of the corticospinal tract (CST), FA value of bilateral CST was measured at the level of posterior limb (PL) of the internal capsule (IC) and the cerebral peduncle of the midbrain, respectively, and statistical analysis was performed. Results Focal slight low signal intensity on T 1WI and high signal intensity (hyperintense to gray matter) on T 2WI was demonstrated in 6 ALS cases (42.9%) in bilateral PL of the IC, and the high signal was longitudinally continuous from the PL to the cerebral peduncle on T 2WI coronal plane, corresponding to the course of CST. In another 8 ALS cases (57.1%), the focal slight low signal intensity on T 1WI and slight high signal intensity (isointense to gray matter) on T 2WI was revealed in bilateral PL of the IC. No abnormal contrast enhancement was detected in the 2 cases. In control group, the focal slight low signal intensity on T 1WI and slight high signal intensity (isointense to gray matter) on T 2WI was demonstrated in all 12 subjects in bilateral PL of the IC. FA values of the patient group were significantly lower than that of the control group at the level of the PL of the IC (F=7.38, P<0.01) and the cerebral peduncle (F=7.31, P=0.01), respectively. Conclusion Clinical information must be considered when diagnosing ALS by using conventional MR imaging. The decreased FA value in CST indicates the neuronal degeneration and associated demyelination in ALS patients. DTI can noninvasively detect and assess CST and its potential disorder in vivo, thus providing useful information in diagnosing and further understanding ALS.