ReviewSilent brain infarcts: a systematic review
Introduction
The symptoms and signs of transient ischemic attack or stroke have long defined cerebrovascular disease of the brain. However, the results of neuropathological studies in highly selected populations have shown that vascular disease manifesting as infarcts can result in injury to the brain in the absence of transient ischemic attack or stroke.1 The development of sophisticated brain-imaging techniques, initially with CT and subsequently with MRI, has enabled similar observations to be made in groups of patients and in healthy people and has forced a rethink of how to define cerebrovascular disease. In this review, we concentrate on one imaging modality (MRI) and one finding that is indicative of brain vascular disease (infarct) in selected patients and otherwise healthy people without a history of transient ischemic attack or stroke to explain the imaging findings. We present an overview of the frequency of these MRI-defined silent brain infarcts, their risk factors, and their consequences. Because they are common and associated with adverse health outcomes, these brain infarcts, which have often been considered as benign accompaniments to ageing, demand greater attention from those trying to control the deleterious effects of vascular disease in the brain.
Section snippets
Search strategy and selection criteria
Articles dating from 1966 to November 2006 were identified through searches of PubMed with the following terms: “silent brain infarcts”, “silent cerebral infarction”, “silent ischaemic lesions”, and “silent lacunes”. We limited searches to adult populations and papers written in English. The PubMed searches identified 313 articles in total. We also searched in the reference lists of relevant publications for further studies, resulting in another 34 articles. We restricted our systematic review
Detection
Infarcts are visible as focal lesions with roughly the same intensity as cerebrospinal fluid on both CT and MRI (figure 1). The sensitivity to detect infarcts is better for MRI compared with CT because of the improvements in MRI techniques with stronger field magnets, thinner slices, and different pulse sequences. This greater sensitivity is particularly true for small lesions located in the basal ganglia, which are often visible only on T2-weighted MRI scans. Studies using CT to detect silent
Conclusion
Silent brain infarcts are common not only in selected patients but also in the general population of elderly people; they are far more common than stroke, both with respect to prevalence and incidence. Cardiovascular risk factors known to increase the risk of stroke are also associated with silent brain infarcts, with hypertension being, by far, the strongest modifiable risk factor identified to date. Therefore, silent brain infarcts might differ from symptomatic infarcts only with respect to
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