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Published on: March 7, 2019
One Size Does Not Fit All: Micro-, Meso-, and Macrobleeds in Cerebral Amyloid Angiopathy
Emma A Koemans1, Thijs W van Harten2, Sabine Voigt1
1Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands.
Introduction:
MRI rating criteria for small vessel disease markers include definitions for microbleeds and macrobleeds but do not account for small (<10 mm) hemorrhages with a cystic cavity and/or irregular shape. Such hemorrhages, however, are often present in patients with cerebral amyloid angiopathy (CAA). In this study, we aimed to investigate the frequency, diameter, and volume distribution of these hemorrhages (which we called mesobleeds) in patients with CAA.
Methods:
We selected participants with Dutch-type hereditary CAA (D-CAA) and sporadic CAA (sCAA) and scored microbleeds, mesobleeds, and macrobleeds on 3T susceptibility-weighted images MRI. Hemorrhage diameter and volume were calculated in a subset of participants using a semi-automatic tool; their distribution was evaluated on a logarithmic scale.
Results:
We included 25 participants with D-CAA (mean age 56 years) and 25 with sCAA (mean age 73 years). In total, 11,007 microbleeds, 602 mesobleeds, and 195 macrobleeds were observed. Eighty-two percent of participants had ≥1 mesobleed. Hemorrhage diameter and volume were calculated in four participants with 272 microbleeds (median diameter 1.52 mm, volume 0.004 mL), 84 mesobleeds (median diameter 5.61 mm, volume 0.06 mL), and 37 macrobleeds (median diameter 19.58 mm, volume 1.33 mL). Mesobleed diameter and volume were larger than microbleeds (optimal cut-off 0.02 mL) but showed overlap with macrobleeds.
Conclusion:
Hemorrhages <10 mm with an irregular shape and/or cystic cavity are frequently found in participants with CAA and have a distinct diameter and volume distribution. We propose to name these hemorrhage mesobleeds and to rate them separately from micro- and macrobleeds. Future research is necessary to investigate their pathophysiology and prognostic value.
Insights
Researchers identified a new type of brain hemorrhage, termed mesobleeds, frequently found in cerebral amyloid angiopathy (CAA) patients. These distinct hemorrhages, smaller than macrobleeds but larger than microbleeds, warrant separate classification in MRI assessments.
Area of Science:
- Neurology
- Radiology
- Vascular Neurology
Background:
- Current MRI criteria for small vessel disease lack definitions for specific hemorrhage types common in cerebral amyloid angiopathy (CAA).
- Small hemorrhages (<10 mm) with cystic or irregular features are frequently observed in CAA patients but are not adequately characterized.
Purpose of the Study:
- To investigate the frequency, diameter, and volume distribution of previously unclassified small hemorrhages in patients with CAA.
- To propose a new classification for these hemorrhages, termed 'mesobleeds', distinct from microbleeds and macrobleeds.
Main Methods:
- Participants with Dutch-type hereditary CAA (D-CAA) and sporadic CAA (sCAA) underwent 3T susceptibility-weighted imaging MRI.
- Microbleeds, mesobleeds, and macrobleeds were scored; hemorrhage diameter and volume were calculated in a subset using a semi-automatic tool.
Main Results:
- A total of 11,007 microbleeds, 602 mesobleeds, and 195 macrobleeds were observed across 50 participants (25 D-CAA, 25 sCAA).
- Eighty-two percent of participants had at least one mesobleed; mesobleeds had a median diameter of 5.61 mm and volume of 0.06 mL.
- Mesobleed dimensions were larger than microbleeds but overlapped with macrobleeds, indicating a distinct category.
Conclusions:
- Hemorrhages <10 mm with irregular shapes or cystic cavities are common in CAA and are proposed to be classified as 'mesobleeds'.
- Mesobleeds possess unique diameter and volume distributions, necessitating separate rating from micro- and macrobleeds in MRI.
- Further research is required to elucidate the pathophysiology and prognostic significance of mesobleeds in CAA.
