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Stroke. 2009 Jul;40(7):2382-6. doi: 10.1161/STROKEAHA.109.548974. Epub 2009 May 14.

Microbleeds versus macrobleeds: evidence for distinct entities.

Author information

1
MGH Stroke Research Center, Harvard Medical School, Boston, MA 02114, USA. sgreenberg@partners.org

Abstract

BACKGROUND AND PURPOSE:

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.

METHODS:

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).

RESULTS:

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).

CONCLUSIONS:

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.

PMID:
19443797
PMCID:
PMC2758289
DOI:
10.1161/STROKEAHA.109.548974
[Indexed for MEDLINE]
Free PMC Article

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