Greenberg Steven M, Nandigam R N Kaveer, Delgado Pilar, Betensky Rebecca A, Rosand Jonathan, Viswanathan Anand, Frosch Matthew P, Smith Eric E
MGH Stroke Research Center, Harvard Medical School, Boston, MA 02114, USA.
Stroke. 2009 Jul;40(7):2382-6. doi: 10.1161/STROKEAHA.109.548974. Epub 2009 May 14.
Small, asymptomatic microbleeds commonly accompany larger symptomatic macrobleeds. It is unclear whether microbleeds and macrobleeds represent arbitrary categories within a single continuum versus truly distinct events with separate pathophysiologies.
We performed 2 complementary retrospective analyses. In a radiographic analysis, we measured and plotted the volumes of all hemorrhagic lesions detected by gradient-echo MRI among 46 consecutive patients with symptomatic primary lobar intracerebral hemorrhage diagnosed as probable or possible cerebral amyloid angiopathy. In a second neuropathologic analysis, we performed blinded qualitative and quantitative examinations of amyloid-positive vessel segments in 6 autopsied subjects whose MRI scans demonstrated particularly high microbleed counts (>50 microbleeds on MRI, n=3) or low microbleed counts (<3 microbleeds, n=3).
Plotted on a logarithmic scale, the volumes of 163 hemorrhagic lesions identified on scans from the 46 subjects fell in a distinctly bimodal distribution with mean volumes for the 2 modes of 0.009 cm(3) and 27.5 cm(3). The optimal cut point for separating the 2 peaks (determined by receiver operating characteristics) corresponded to a lesion diameter of 0.57 cm. On neuropathologic analysis, the high microbleed-count autopsied subjects showed significantly thicker amyloid-positive vessel walls than the low microbleed-count subjects (proportional wall thickness 0.53+/-0.01 versus 0.37+/-0.01; P<0.0001; n=333 vessel segments analyzed).
These findings suggest that cerebral amyloid angiopathy-associated microbleeds and macrobleeds comprise distinct entities. Increased vessel wall thickness may predispose to formation of microbleeds relative to macrobleeds.
小的无症状微出血通常伴随较大的有症状的大出血。目前尚不清楚微出血和大出血是代表单一连续体中的任意类别，还是具有不同病理生理学的真正不同事件。
我们进行了两项互补的回顾性分析。在影像学分析中，我们测量并绘制了46例连续诊断为可能或疑似脑淀粉样血管病的有症状原发性脑叶脑出血患者中，通过梯度回波MRI检测到的所有出血性病变的体积。在第二项神经病理学分析中，我们对6例尸检对象的淀粉样蛋白阳性血管段进行了盲法定性和定量检查，这些对象的MRI扫描显示微出血计数特别高（MRI上>50处微出血，n = 3）或微出血计数低（<3处微出血，n = 3）。
以对数标度绘制，46例受试者扫描中识别出的163个出血性病变的体积呈明显的双峰分布，两种模式的平均体积分别为0.009 cm³和27.5 cm³。分离两个峰值的最佳切点（由受试者工作特征确定）对应于病变直径0.57 cm。在神经病理学分析中，高微出血计数的尸检对象显示淀粉样蛋白阳性血管壁明显比低微出血计数的对象厚（比例壁厚0.53±0.01对0.37±0.01；P<0.0001；分析了333个血管段）。
这些发现表明，脑淀粉样血管病相关的微出血和大出血构成不同的实体。相对于大出血，血管壁厚度增加可能易导致微出血形成。
