肾上腺脑白质营养不良的MR功能成像表现分析

Analysis of functional MR imaging patterns in adrenoleukodystrophy

目的探讨磁共振扩散加权成像(DWI)的信号及波谱(MRS)的代谢异常变化与肾上腺脑白质营养不良(ALD)病理、生化改变的对应性。方法分析6例血浆极长链脂肪酸增高证实的ALD的病变不同区域表观扩散系数(ADC)和磁共振波谱N乙酰天门冬氨酸(NAA)、胆碱复合物(Cho)和乳酸(Lac)的代谢变化,比较病变的位置不同和时间不同在ADC值和代谢变化中的差异。结果病灶最早发生的枕顶叶脑白质区域,DWI信号很低,ADC值最高(2.400×10-3mm2/s,F=7.31,P=0.003),NAA/Cr和NAA/Cho降低(0.62±0.24,F=4.00,P=0.02;0.32±0.16,F=6.75,P=0.02),Cho/Cr和Lac/Cr增高(1.96±0.53,F=3.53,P=0.03;0.28±0.24,F=3.22,P=0.04)。在病灶向前扩展的区域中,DWI信号最高,而ADC值最低[(0.749～0.752)×10-3mm2/s,F=7.31,P=0.003],灶周近区NAA/Cr和NAA/Cho降低较远区明显(q2=-0.23,p2=0.047;q2=-0.23,p2=0.02),Cho/Cr和Lac/Cr的增高无统计学意义(q2=0.34,p2=0.19;q2=0.11,p2=0.17)。结论磁共振功能成像能够动态观察营养不良的脑白质的空间时间演变顺序。陈旧性病灶,ADC值升高,Cho和Lac均升高,NAA下降明显。进展区的病灶,ADC明显降低,Cho和Lac的升高变化较前者并不显著,残存的神经元和轴索的保留使NAA的水平部分下降。

Objective To discuss the parallelism of signals in MR diffusion-weighted imaging(DWI) and metabolic abnormity in proton MR spectroscopy(~1HMRS) with pathologic and biochemical changes in adrenoleukodystrophy (ALD). Methods DWI and ~1H MRS examination were performed in 6 cases with ALD proven by serum VLCFA, comparing ADC and relative ratio values of each metabolite in different regions of lesion with normal white matter.Results Initial lesions in occipital-parietal lobes showed very low signals on DWI and the highest ADC values(2.400×10~ -3 mm^2/s,F=7.31,P=0.003), the ratios of NAA/Cr and NAA/Cho were lower(0.62±0.24,F=4.00,P=0.02; 0.32±0.16,F=6.75,P=0.02),and Cho/Cr and Lac/Cr were higher than normal white matter(1.96±0.53,F=3.53,P=0.03; 0.28±0.24,F=3.22,P=0.04). On expanding regions to frontal lobe, the signal became highest and ADC values was lowest[(0.749-0.752)×10~ -3 mm^2/s,F=7.31,P=0.003].The depressed tendency of NAA/Cr and NAA/Cho in adjacent lesion was distinct than that of remote lesion (q_2=-0.23,P_2=0.047; q_2=-0.23,P_2=0.02). There was no significant difference in the increase of Cho/Cr and Lac/Cr ratios (q_2=0.34,P_2=0.19; q_2=0.11,P_2=0.17).Conclusion MRS offers a useful method for dynamic observation of spatio-temporal changes in ALD. ADC values and choline, lactic acid levels increase in obsolete lesions whereas NAA levels decrease distinctly. In expanding lesion, ADC values decrease markedly, while the elevation of Choline and Lactic acid is not significant in adjacent region. NAA levels decrease moderately because of remnant neuron and axon.