MedicalResearch.com Interview with:
Christopher Chen, FRCP
Department of Pharmacology
Yong Loo Lin School of Medicine
Memory Aging and Cognition Center
National University Health System
Saima Hilal, PhD
Department of Pharmacology, National University of Singapore
Department of Radiology, Epidemiology and Nuclear Medicine
Erasmus Medical Center, Rotterdam, the Netherlands
MedicalResearch.com: What is the background for this study?
Response: Cerebral microinfarcts (CMIs) are defined as small (usually <1 mm) regions of ischemic change found in the brain which are not readily visible on gross examination or on standard 1.5-T magnetic resonance imaging (MRI). On microscopy they appear as foci of neuronal loss, gliosis, pallor, or cysts.
Previous post mortem studies have shown that the presence of CMIs is relatively common in elderly individuals without dementia (24%) but more common in patients diagnosed with Alzheimer disease (43%) or vascular dementia (62%).
Whilst a single CMI is likely to be “silent” as the region of brain affected is probably too small to produce symptoms or neurologic deficits, however, as a large number of CMIs exist in many individuals, especially in the cerebral cortex and watershed areas, the overall effect has clinical importance – as shown by neuropathologic studies which demonstrate an important role of CMIs in cognitive dysfunction and dementia. However in vivo studies have been hampered by the inability to detect CMIs reliably on neuroimaging, leading to CMIs being termed “invisible” during life.
The advent of high spatial-definition 7-T MRI enabled the identification of cortical Cerebral microinfarcts in-vivo and importantly a study that directly compared 7-T and 3-T MRIs in the same patients reported that 3-T MRI detected about 1/3 of the lesions found on 7-T MRIs, suggesting that 3-T MRIs, which are more accessible than 7-T, may be able to detect larger cortical CMIs with a lower limit of approximately 1 mm in diameter.
Our group has made major contributions recently on the clinical associations of 3T MRI detected cortical CMIs in patients from memory clinics as well as in community based subjects. Associations were found with age, vascular risk factors, other MRI markers of cerebrovascular disease as well as cognition. However, the causes of CMIs remain unclear and may be heterogeneous with microembolism, microthrombosis, and foci of inflammation as possible causative factors.