Cerebral Microbleeds: Detection, Mechanisms and Clinical Challenges

Abstract

In the last decade or so, cerebral microbleeds (CMBs) – tiny perivascular hemorrhages seen as small, well-demarcated, hypointense, rounded lesions on MRI sequences that are sensitive to magnetic susceptibility – have generated increasing interest among neurologists and clinical stroke researchers. As MRI techniques become more sophisticated, CMBs are increasingly detected in various patient populations (including all types of stroke, Alzheimer’s disease and vascular cognitive impairment) and healthy community-dwelling older people. Their presence raises many clinical dilemmas and intriguing pathophysiological questions. CMBs are emerging as an important new manifestation and diagnostic marker of cerebral small-vessel disease. They are a potential predictor of future intracerebral hemorrhage risk, a possible contributor to cognitive impairment and dementia and a potential key link between vascular and degenerative pathologies. In this article, we discuss the available pathological, neuroimaging and clinical studies in the field, and we provide a modern overview of the clinical and pathophysiological implications of CMBs in different disease settings.

Cerebral microbleeds and cognition in cerebrovascular disease: An update

“…CMBs are increasingly detected in various patient populations and disease settings, including first-ever and recurrent ischaemic or haemorrhagic stroke, Alzheimer's disease, VCI and healthy older people [6,14,15]. Histopathological correlation has shown that radiologically-defined CMBs are quite specific for small collections of blood-breakdown products (in particular, haemosiderin contained within perivascular macrophages), adjacent to abnormal small vesselsmainly affected by hypertensive arteriopathy or CAA [16].…”

“…In addition, cerebral microbleeds (CMBs) -small, perivascular haemorrhages seen as well-demarcated, hypointense, rounded lesions on MRI sequences sensitive to magnetic susceptibility ( Fig. 1) -have emerged as an important new manifestation and diagnostic marker of small vessel pathology [6,7]. However, their clinical impact on cognition remains an active field of research [6].…”

“…1) -have emerged as an important new manifestation and diagnostic marker of small vessel pathology [6,7]. However, their clinical impact on cognition remains an active field of research [6]. This review considers recent evidence on how CMBs may be relevant in the study of cognitive impairment in populations of individuals with -or at risk of -cerebrovascular disease (Table 1).…”

Relationship Between Radiation Dose and Microbleed Formation in Patients With Malignant Glioma

“…Studies with primate [9] and murine models [10], as well as human autopsy studies [11,12], have demonstrated that microvascular damage is a prominent pathologic component of radiation-induced brain injury, with endothelial degeneration leading to the formation cerebral microbleeds (CMBs). CMBs have also been observed in elderly patients without known underlying pathology [13,14], as well as in other degenerative central nervous system conditions, including cerebral amyloid angiopathy (CAA) associated with Alzheimer's disease and vascular cognitive impairment [11], where they have been linked to cognitive dysfunction [15][16][17][18].…”

“…CMBs have also been observed in elderly patients without known underlying pathology [13,14], as well as in other degenerative central nervous system conditions, including cerebral amyloid angiopathy (CAA) associated with Alzheimer's disease and vascular cognitive impairment [11], where they have been linked to cognitive dysfunction [15][16][17][18]. Thus, quantification of CMB characteristics may serve as a valuable metric for radiation-induced vasculopathy and resultant cognitive decline.…”