Liu Lan-Xiang, Du Dan, Zheng Tao, Fang Yuan, Chen Yan-Sheng, Yi Hui-Ling, He Qing-Yuan, Gao Da-Wei, Shi Qing-Lei
Department of Magnetic Resonance Imaging, First Hospital of Qinhuangdao, Qinhuangdao, Hebei Province, China.
Department of Radiology, Peking University Third Hospital, Beijing, China.
Neural Regen Res. 2017 Sep;12(9):1485-1491. doi: 10.4103/1673-5374.213559.
Dopamine content in the basal ganglia is strongly associated with the degree of dopaminergic neuron loss in the substantia nigra pars compacta. Symptoms of Parkinson's disease might not arise until more than 50% of the substantia nigra pars compacta is lost and the dopamine content in the basal ganglia is reduced by more than 80%. Greater diagnostic sensitivity and specificity would allow earlier detection of Parkinson's disease. Diffusion tensor imaging is a recently developed magnetic resonance imaging technique that measures mean diffusivity and fractional anisotropy, and responds to changes in brain microstructure. When the microscopic barrier (including cell membranes, microtubules and other structures that interfere with the free diffusion of water) is destroyed and extracellular fluid volume accumulates, the mean diffusivity value increases; when the integrity of the microstructure (such as myelin) is destroyed, fractional anisotropy value decreases. However, there is no consensus as to whether these changes can reflect the early pathological alterations in Parkinson's disease. Here, we established a rat model of Parkinson's disease by injecting rotenone (or sunflower oil in controls) into the right substantia nigra. Diffusion tensor imaging results revealed that in the stages of disease, at 1, 2, 4, and 6 weeks after rotenone injection, fractional anisotropy value decreased, but mean diffusivity values increased in the right substantia nigra in the experimental group. Fractional anisotropy values were lower at 4 weeks than at 6 weeks in the right substantia nigra of rats from the experimental group. Mean diffusivity values were markedly greater at 1 week than at 6 weeks in the right corpus striatum of rats from the experimental group. These findings suggest that mean diffusivity and fractional anisotropy values in the brain of rat models of Parkinson's disease 4 weeks after model establishment can reflect early degeneration of dopaminergic neurons. The change in fractional anisotropy values after destruction of myelin integrity is likely to be of greater early diagnostic significance than the change in mean diffusivity values.
基底神经节中的多巴胺含量与黑质致密部多巴胺能神经元的损失程度密切相关。直到黑质致密部损失超过50%且基底神经节中的多巴胺含量降低超过80%，帕金森病的症状才可能出现。更高的诊断敏感性和特异性将有助于更早地检测出帕金森病。扩散张量成像（DTI）是一种最近开发的磁共振成像技术，它测量平均扩散率和分数各向异性，并对脑微观结构的变化做出反应。当微观屏障（包括细胞膜、微管和其他干扰水自由扩散的结构）被破坏且细胞外液体积积聚时，平均扩散率值增加；当微观结构（如髓鞘）的完整性被破坏时，分数各向异性值降低。然而，对于这些变化是否能反映帕金森病的早期病理改变尚无共识。在此，我们通过向右侧黑质注射鱼藤酮（对照组注射向日葵油）建立了帕金森病大鼠模型。扩散张量成像结果显示，在疾病阶段，鱼藤酮注射后1、2、4和6周，实验组右侧黑质的分数各向异性值降低，但平均扩散率值增加。实验组大鼠右侧黑质在4周时的分数各向异性值低于6周时。实验组大鼠右侧纹状体在1周时的平均扩散率值明显高于6周时。这些发现表明，帕金森病大鼠模型在模型建立4周后脑内的平均扩散率和分数各向异性值可反映多巴胺能神经元的早期退变。髓鞘完整性破坏后分数各向异性值的变化可能比平均扩散率值的变化具有更大的早期诊断意义。
