Infarcts in brain
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Brain Infarcts: Insights from Recent Research
Genetic Associations with Brain Infarcts
Genome-Wide Association Studies (GWAS) and MRI-Defined Brain Infarcts
Recent studies have explored the genetic underpinnings of brain infarcts using genome-wide association studies (GWAS). A significant study involving the CHARGE consortium identified a notable association between the single nucleotide polymorphism (SNP) rs2208454 and a reduced risk of MRI-defined brain infarcts. This SNP is located in the MACROD2 gene and the downstream region of the FLRT3 gene. Each copy of the minor allele was associated with a 24% lower risk of MRI infarcts. However, replication efforts in independent samples did not confirm these findings, suggesting the need for further research to validate these associations.
Pathogenesis and Types of Brain Infarcts
Watershed Infarcts
Watershed infarcts occur in the border zones between major cerebral arteries, such as the anterior and middle cerebral arteries. These infarcts can result from systemic hypotension or microembolism and account for approximately 10% of all brain infarcts. They are characterized by their location and can be either pale or hemorrhagic, although the hemorrhagic component is usually not prominent.
Lower Brainstem Infarcts
Infarcts in the lower brainstem can be classified into six topographical types based on MRI patterns: small midlateral, dorsolateral, inferolateral, large inferodorsolateral, dorsal, and paramedian infarcts. These types are associated with specific neurological syndromes, such as Wallenberg's syndrome and crossed tongue and sensorimotor hemiplegia. Atheromatosis is the most common cause, followed by vertebral artery dissection and cardioembolism.
Incidence and Impact on Cognitive Function
Incidence and Risk Factors
A longitudinal study found that 21% of participants developed new brain infarcts over an average follow-up of 5.2 years. Men were at a higher risk than women. Both incident and prevalent infarcts were associated with steeper cognitive decline and an increased risk of dementia, particularly subcortical infarcts, which had the highest risk of leading to dementia.
Silent Brain Infarcts
Silent brain infarcts, detected through MRI without clinical stroke symptoms, are prevalent in up to 50% of certain patient populations. These infarcts are primarily lacunes caused by hypertensive small-vessel disease. Despite their lack of overt symptoms, silent infarcts are linked to subtle cognitive and physical deficits and significantly increase the risk of subsequent stroke and dementia.
Clinical-Pathologic Correlations
Arterial Border-Zone Infarcts
Arterial border-zone infarcts, often resulting from hemodynamic crises, can lead to specific neurological syndromes depending on the affected brain regions. The most common syndrome involves bilateral brachial paralysis, known as the "man-in-a-barrel" syndrome, due to infarcts in the border zone between the anterior and middle cerebral arteries.
Histologic Assessment of Recent Brain Infarcts
Histological examination of brain infarcts can help determine their age. Four distinct periods within the first month of infarct evolution have been identified, characterized by specific cellular changes such as the presence of eosinophilic neurons, macrophages, and astrocytic proliferation.
Conclusion
Brain infarcts, whether symptomatic or silent, have significant implications for cognitive function and overall brain health. Genetic studies, such as those involving GWAS, provide insights into potential risk factors, while clinical and histological studies help understand the pathogenesis and progression of these infarcts. Continued research is essential to develop effective prevention and treatment strategies to mitigate the impact of brain infarcts on cognitive decline and dementia.
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