Cerebral blood flow and metabolism in silent brain infarction and related cerebrovascular disorders

The appropriate management of silent stroke requires better understanding of the haemodynamic status in the brain. However, only a few studies have examined cerebral blood flow and metabolism in subjects with silent stroke. Positron emission tomography demonstrated a slight decrease in cortical blood flow with an increase in oxygen extraction fraction (ie misery perfusion) in subjects with silent brain infarction, whereas both cerebral blood flow and oxygen metabolism decreased in patients with symptomatic brain infarction (matched hypoperfusion). These findings confirm that brain circulation is haemodynamically compromised in subjects with silent stroke. Another important point is that subcortical silent stroke may induce a reduction in cortical blood flow and metabolism by a disconnection mechanism (ie diaschisis) between the cortex and the subcortical structures. Silent infarction is not innocuous in terms of compromised cerebral circulation, which may lead to cognitive decline or subsequent clinical stroke. In the future, further developments in functional imaging will permit a more sophisticated analysis of brain circulation and metabolism in silent stroke.