Cerebral microbleeds and stroke: more questions than answers

Abstract

CMBs are a radiological biomarker of cerebral small vessel disease. They are seen on blood-sensitive MRI sequences such as T2*-weighted gradient-recalled echo (T2*-GRE) or susceptibility-weighted imaging (SWI) 1,2,3,4,5,6 . They are small (usually <5 mm in diameter), rounded or oval lesions of low signal intensity in the brain parenchyma 1,2,3,4,7,8 . CMBs represent haemosiderin deposits contained within macrophages in the microvascular perivascular spaces on histopathological examinations 1,2,3,4,9 , and develop as a result of leakage of red blood cells secondary to rupture of the walls of small arteries, arterioles or capillaries 1,2,10 . Whether the rupture of a small vessel results in a microbleed or a larger macrobleed is believed to depend on different vasculopathic features and environmental exposure 5,7 . Two distinct patterns of microangiopathy are noted on histopathological testing in the blood vessels located near CMBs: lipohyalinosis and cerebral amyloid angiopathy (CAA). The pattern of microangiopathy appears to determine the pattern of anatomical distribution of CMBs;