Diaschisis after stroke: a novel approach with arterial spin labeling (ASL) MRI

描述（由申请人提供）：本研究的总体目标是使用连续动脉自旋标记、CASL、灌注MRI来表征脑缺血并确定其对亚急性脑卒中后偏瘫的影响。尽管急性中风的治疗和预防有所改善，但中风仍然是世界范围内死亡的主要原因。患者在恢复的程度上表现出相当大的可变性，而这种可变性的机制在很大程度上仍然未知。近一个世纪前，有人提出了一种被称为“再生”的机制，用来解释部分初始赤字和部分从赤字中恢复的能力。脑缺血是指与受伤部位相连的未受伤脑区脑血流减少。动物模型表明，脑血流量的减少是连接区域神经元活动减少的结果。在这个框架内，最初的缺陷是由于损伤部位的骨裂和功能丧失的结合，而当骨裂逆转时就会恢复。以前研究这种人类现象的尝试依赖于PET和SPECT，这两种方法价格昂贵，而且不广泛使用，并且需要注射放射性示踪剂，限制了使用的频率和实用性。因此，关于脑缺血的研究相对较少，因此其与卒中缺陷和卒中恢复的相关性仍有待确定。在这里，我们建议使用动脉自旋标记（ASL）来研究偏瘫卒中后亚急性期和慢性期患者的脑缺血。ASL是一种量化血流的无创MR方法。迄今为止，它已被用于测量因血管闭塞性疾病而受损的脑血流（CBF）。在这里，我们提出了一种新的应用ASL来检测由于神经元活动减少而导致的脑血流减少。这项资助的主要目的是证明对侧小脑（交叉小脑裂）和对侧半球CBF的减少。然后，我们将这些变化与中风后3至4周的初始运动缺陷和6个月的恢复程度联系起来。

DESCRIPTION (provided by applicant): The overall goal of this study is to use continuous arterial spin labeling, CASL, perfusion MRI to characterize diaschisis and determine its contribution to hemiparesis after subacute stroke. Stroke remains the leading cause of death worldwide despite improvements in acute stroke treatment and prevention. Patients show considerable variability in the degree to which they recover and the mechanisms underlying this variability are still largely unknown. One mechanism, termed diaschisis, was proposed almost a century ago to explain part of the initial deficit and the ability to partially recover from it. Diaschisis refers to a reduction of cerebral blood flow in uninjured brain regions that are connected to the area of injury. Animal models suggest that the reduction in cerebral blood flow is the result of decreased neuronal activity in the connected areas. Within this framework, the initial deficit is due to combination of diaschisis and the loss of function at the lesion location, whereas recovery occurs as diaschisis reverses. Previous attempts to study this phenomenon in humans have relied on PET and SPECT, which are expensive, not widely available, and require injection of radioactive tracers, limiting the frequency and practicality of use. As a result, there have been relatively few studies of diaschisis and thus its relevance to stroke deficit and stroke recovery remains to be determined. Here we propose to use arterial spin labeling, ASL, to investigate diaschisis in patients in the subacute and then chronic phases after hemiparetic stroke. ASL is non-invasive MR method that quantifies blood flow. To date it has been used to measure cerebral blood flow, CBF, that has been compromised by vascular occlusive disease. Here we propose a novel application of ASL for detection of decreases in CBF due to reduction in neuronal activity. The main aim of this grant is to demonstrate reductions in CBF in the contralateral cerebellum (crossed cerebellar diaschisis) and in the contralesional hemisphere. We will then correlate these changes with initial motor deficit in 3 to 4 weeks after stroke and with degree of recovery at 6 months.