Dichgans Martin, Pütz Benno, Boos Daniel, Auer Dorothee P
Department of Neurology, Klinikum Grosshadern, Ludwig-Maximilians-Universität, AG NMR, D-80804 Munich, Germany.
AJNR Am J Neuroradiol. 2003 Jun-Jul;24(6):1083-9.
Subcortical signal intensity abnormalities and lacunar infarcts are the radiologic hallmark of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. MR diffusion studies reveal abnormalities in lesions and also within normal appearing white matter. To further characterize the underlying pathologic abnormality, we evaluated the role of subvoxel free fluid in brain with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy on diffusion parameters and physical disability and analyzed the interrelation between diffusion variables and nonlacunar T2 lesion load.
Mean diffusivity maps from fluid-attenuated and standard diffusion images of 13 patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy and seven age-matched control participants were compared by means of histogram analysis for three tissue compartments (whole brain parenchyma, normal appearing brain tissue, and nonlacunar lesions) by using a semiautomated region growing algorithm to define whole brain parenchyma and lesions on fluid-attenuated images.
In both patients and control participants, the average mean diffusivity of whole brain parenchyma was lower on fluid-attenuated than on standard images (P <.001). Average mean diffusivity and peak location for all compartments were significantly elevated in patients (P <.001) and higher for lesions than for normal appearing brain tissue on both types of images (P <.001). The difference between standard and fluid-attenuated average mean diffusivity of normal appearing brain tissue, reflecting the subvoxel free fluid content, was elevated in patients (P <.05) and correlated closely with the Rankin score (Spearman's rank correlation coefficient = 0.889, P <.001). Average mean diffusivity of whole brain parenchyma and normal appearing brain tissue correlated strongly with the nonlacunar T2 lesion load (Pearson's correlation coefficient = 0.743-0.928, P <.005).
This study shows that standard diffusion measurements are contaminated by free fluid partial volume effects for patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy and for control participants. It also provides evidence of a clinical significance of increased subvoxel free fluid in normal appearing brain with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, which may be more important than either global atrophy, increased diffusivity or, T2 lesion load.
皮质下信号强度异常和腔隙性梗死是伴有皮质下梗死和白质脑病的常染色体显性遗传性脑动脉病的影像学特征。磁共振扩散研究显示病变部位以及正常白质内均存在异常。为进一步明确潜在的病理异常，我们评估了伴有皮质下梗死和白质脑病的常染色体显性遗传性脑动脉病患者脑内亚体素游离液体在扩散参数和身体残疾方面的作用，并分析了扩散变量与非腔隙性T2病变负荷之间的相互关系。
通过直方图分析比较了13例伴有皮质下梗死和白质脑病的常染色体显性遗传性脑动脉病患者以及7名年龄匹配的对照者的液体衰减和标准扩散图像的平均扩散率图，针对三个组织区域（全脑实质、正常脑组织和非腔隙性病变），使用半自动区域生长算法在液体衰减图像上定义全脑实质和病变。
在患者和对照者中，全脑实质在液体衰减图像上的平均扩散率均低于标准图像（P <.001）。患者所有区域的平均扩散率和峰值位置均显著升高（P <.001），且在两种图像上病变区域的平均扩散率均高于正常脑组织（P <.001）。反映亚体素游离液体含量的正常脑组织在标准图像和液体衰减图像上平均扩散率的差异在患者中升高（P <.05），且与Rankin评分密切相关（Spearman等级相关系数 = 0.889，P <.001）。全脑实质和正常脑组织的平均扩散率与非腔隙性T2病变负荷密切相关（Pearson相关系数 = 0.743 - 0.928，P <.005）。
本研究表明，对于伴有皮质下梗死和白质脑病的常染色体显性遗传性脑动脉病患者及对照者，标准扩散测量受到游离液体部分容积效应的影响。研究还提供了证据，表明伴有皮质下梗死和白质脑病的常染色体显性遗传性脑动脉病患者正常脑组织中亚体素游离液体增加具有临床意义，这可能比整体萎缩、扩散率增加或T2病变负荷更为重要。
