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Cerebral Microbleeds, Small-Vessel Disease of the Brain, Hypertension, and Cognition

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Part of the book series: Clinical Hypertension and Vascular Diseases ((CHVD))

Abstract

Cerebral microbleeds (CMB) have been increasingly recognized on neuroimaging since the widespread application of magnetic resonance imaging (MRI) techniques tailored to detect foci of magnetic susceptibility. CMB are most often clinically asymptomatic and are a result of rupture of small blood vessels in basal ganglia or subcortical white matter (AJNR Am J Neuroradiol. 1999;20:637–42; Lancet Neurol. 2009;8:165–74; Stroke. 2006;37:550–5; Brain. 2007;130:1988–2003). CMB were first described after the clinical use of gradient-echo (GRE) or T2*-weighted MRI (AJNR Am J Neuroradiol. 1999;20:637–42; Neuroradiology. 1994;36:504–8; AJNR Am J Neuroradiol. 1996;17:573–8). GRE MRI is a technique highly sensitive in the detection of old and recent cerebral hemorrhage (AJNR Am J Neuroradiol. 1999;20:637–42; AJNR Am J Neuroradiol. 1996;17:573–8). The reduction of the signal on GRE sequences is caused by hemosiderin, a blood breakdown product which causes magnetic susceptibility-induced dephasing leading to T2* signal loss. CMB appear larger on GRE sequences as compared to the actual tissue lesions because of the so-called blooming effect of the MR signal at the border of these lesions (Neuroradiology. 2004;46:435–43; Acta Radiol. 2003;44:199–205). GRE MRI can detect millimeter-sized paramagnetic blood products (including hemosiderin) in brain parenchyma (Radiology. 1988;168:803–7). As hemosiderin remains in macrophages for many years after hemorrhage (Neurology. 1996;46:1751–4; Curr Opin Neurol. 2000;13:69–73), GRE sequences allow for reliable assessment of an individual’s hemorrhagic burden over time. Furthermore, more recent technical advances in MRI software and hardware have yielded significant improvements in sensitivity, which has led to increased detection of CMB in different populations (AJNR Am J Neuroradiol. 2007;28:316–7; AJNR Am J Neuroradiol. 2009;30:19–30; AJNR Am J Neuroradiol. 2009;30(2):338–43; Neurology. 2008;70:1208–14). Novel techniques such as susceptibility-weighted imaging (SWI) have considerably increased CMB detection rates.

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Viswanathan, A., Chabriat, H., Greenberg, S.M. (2016). Cerebral Microbleeds, Small-Vessel Disease of the Brain, Hypertension, and Cognition. In: Aiyagari, V., Gorelick, P. (eds) Hypertension and Stroke. Clinical Hypertension and Vascular Diseases. Humana Press, Cham. https://doi.org/10.1007/978-3-319-29152-9_17

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