Small subclinical hyperintense lesions are frequently encountered on brain diffusion-weighted imaging (DWI) scans of patients with cerebral amyloid angiopathy (CAA). Interpretation of these DWI+ lesions, however, has been limited by absence of histopathological examination. We aimed to determine whether DWI+ lesions represent acute microinfarcts on histopathology in brains with advanced CAA, using a combined in vivo MRI-ex vivo MRI-histopathology approach. We first investigated the histopathology of a punctate cortical DWI+ lesion observed on clinical in vivo MRI 7 days prior to death in a CAA case. Subsequently, we assessed the use of ex vivo DWI to identify similar punctate cortical lesions post-mortem. Intact formalin-fixed hemispheres of 12 consecutive cases with CAA and three non-CAA controls were subjected to high-resolution 3 T ex vivo DWI and T2 imaging. Small cortical lesions were classified as either DWI+/T2+ or DWI-/T2+. A representative subset of lesions from three CAA cases was selected for detailed histopathological examination. The DWI+ lesion observed on in vivo MRI could be matched to an area with evidence of recent ischemia on histopathology. Ex vivo MRI of the intact hemispheres revealed a total of 130 DWI+/T2+ lesions in 10/12 CAA cases, but none in controls (p = 0.022). DWI+/T2+ lesions examined histopathologically proved to be acute microinfarcts (classification accuracy 100%), characterized by presence of eosinophilic neurons on hematoxylin and eosin and absence of reactive astrocytes on glial fibrillary acidic protein-stained sections. In conclusion, we suggest that small DWI+ lesions in CAA represent acute microinfarcts. Furthermore, our findings support the use of ex vivo DWI as a method to detect acute microinfarcts post-mortem, which may benefit future histopathological investigations on the etiology of microinfarcts.

中文翻译：

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脑淀粉样血管病中弥散加权成像阳性病变的组织病理学。

在患有脑淀粉样血管病（CAA）的患者进行脑弥散加权成像（DWI）扫描时，经常会遇到小的亚临床高强度病变。然而，由于缺乏组织病理学检查，这些DWI +病变的解释受到限制。我们旨在通过结合体内MRI-离体MRI-组织病理学方法来确定DWI +病变是否代表晚期CAA大脑组织病理学上的急性微梗塞。我们首先调查了CAA病例死亡前7天在临床体内MRI上观察到的点状皮质DWI +病变的组织病理学。随后，我们评估了离体DWI在死后鉴定类似点状皮层皮损的用途。对连续连续12例患有CAA的病例和三个非CAA对照的完整福尔马林固定的半球进行高分辨率的3 T离体DWI和T2成像。小皮层病变被分类为DWI + / T2 +或DWI- / T2 +。从3例CAA病例中选择代表性的病灶进行详细的组织病理学检查。体内MRI观察到的DWI +病变可与组织病理学上最近缺血的证据相匹配。完整半球的离体MRI显示，在10/12 CAA病例中共有130个DWI + / T2 +病变，但在对照组中则没有（P = 0.022）。经组织病理学检查发现的DWI + / T2 +病变为急性微梗塞（分类准确度为100％），其特征是苏木精和曙红上存在嗜酸性神经元，而神经胶质原纤维酸性蛋白染色切片上没有反应性星形胶质细胞。总之，我们建议CAA中小的DWI +病变代表急性微梗塞。此外，我们的研究结果支持使用离体DWI作为检测死后急性微梗塞的方法，这可能会有利于将来对微梗塞病因的组织病理学研究。