MR-Tractography study of the pathogenesis of arousal impairment in hypersomnia

我们应用基于体素的SPM 8统计方法对MRI上获得的FA/ADC图像和灰色/白色图像进行统计，以估计发作性睡病和特发性睡眠过度的脑微结构变化，这两种疾病的主要表现都是白天过度嗜睡。结果显示，无论是否伴有cataemia，发作性睡病患者中脑与觉醒维持相关的神经核团存在的白色物质体积减少，双侧杏仁核和左侧内侧额叶区ADC值升高。睡眠效率与ADC值、FA值呈负相关，主要集中在右边缘区。这些结果表明，轴突改变的程度与睡眠维持系统的紊乱有关。此外，其发病机制可能与右侧中央前回、右侧额下回、右侧楔前叶和左侧小脑扁桃体的异常有关。特发性嗜睡症患者大脑皮层枕、额、颞区沿着远端白色物质FA异常。因此，发作性睡病与特发性嗜睡症的日间过度嗜睡的机制是不同的。

We applied the voxel-based statistic approach by SPM8 for FA/ADC image and gray/white matter images obtained on MRI to estimate the brain microstructural change in narcolepsy and idiopathic hypersomnia, both which chief compliant is excessive daytime sleepiness. As a results, narcolepsy, regardless with or without cataplexy, showed reduced white matter volume of midbrain where the neural nuclei associated with maintenance of arousal exist, higher ADC in bilateral amygdala and left medial frontal area. Sleep efficiency showed negative correlation with ADC and FA in mainly right limbic area. These results indicate that the degree of axonal change is related with the disturbance in sleep maintenance system. Additionally, the pathogenesis of cataplexy might associated with abnormality in right precentral gyrus, right inferior frontal gyrus, right precuneus and left cerebellar tonsil. On the other hand, idiopathic hypersomnia showed FA abnormality in white matter distally along cerebral cortex of occipital, frontal and temporal area. As a conclusion, the mechanism of excessive daytime sleepiness is thought to be distinct between narcolepsy and idhiopathic hypersomnia.