Studies of many aged brains shows that the progression of various types of dementia correlates with a history of many small, unnoticed strokes. These leave behind small infarcts, areas of tissue death in the brain caused by a local blockage of small blood vessels. The brains of people suffering neurodegeneration tend to have more of these infarcts. Is this causative, however? Some of the past evidence is fairly compelling with regard to causation, but this remains an open question: since aging is a global phenomenon many of its aspects should be expected to correlate with one another regardless of any direct linkage.
Here is another recent paper demonstrating the correlation, in which the researchers show off the capabilities of an evolution of magnetic resonance imaging (MRI) technology that is more capable of picking out these small areas of structural damage than has been the case in the past:
Until recently cortical microinfarcts (CMIs) were considered as the invisible lesions in clinical-radiological correlation studies that rely on conventional structural magnetic resonance imaging. The present study investigates the presence of CMIs on 7.0-T magnetic resonance imaging (MRI) in post-mortem brains with different neurodegenerative and cerebrovascular diseases. One hundred-seventy five post-mortem brains, composed of 37 with pure Alzheimer's disease (AD), 12 with AD associated to cerebral amyloid angiopathy (AD-CAA), 38 with frontotemporal lobar degeneration, 12 with amyotrophic lateral sclerosis, 16 with Lewy body disease (LBD), 21 with progressive supranuclear palsy, 18 with vascular dementia (VaD) and 21 controls were examined. According to their size several types of CMIs were detected on 3 coronal sections of a cerebral hemisphere with 7.0-T MRI and compared to the mean CMI load observed on histological examination of one standard separate coronal section of a cerebral hemisphere at the level of the mamillary body.
Overall CMIs were significantly prevalent in those brains with neurodegenerative and cerebrovascular diseases associated to CAA compared to those without CAA. VaD, AD-CAA and LBD brains had significantly more CMIs compared to the controls. While all types of CMIs were increased in VaD and AD-CAA brains, a predominance of the smallest ones was observed in the LBD brains. The present study shows that 7.0-T MRI allows the detection of several types of MICs and their contribution to the cognitive decline in different neurodegenerative and cerebrovascular diseases.