MRI (magnetic resonance imaging) is an incredible technique that was first used to scan patients in the 1970s and 1980s. It uses radio waves, giant magnets, and computational tools to visualize structures inside the human body. The technique is often used to look at the brain and spinal cord and can help detect and diagnose a wide range of diseases. Clinicians may also notice bright, white spots on MRIs of the brain. These are lesions known as white matter hyperintensities (WMH), and they seen in about 20 percent of individuals who are over 60 years old. WMH also become more common as people get older, and by the time people are over age 80, almost everyone has them; an estimated 90 percent of people over 80 have WMHs.
Some research has suggested that WMH can be indicative of thinning or atrophy in the cerebral cortex. Now scientists have shown that this hypothesis is true. The investigators also identified some genetic causes of routine WMH in adults. The findings have been reported in Nature Communications.
"We set out to study WMH and their potential link to cortical atrophy, a core feature in dementia," explained co-corresponding study author Zdenka Pausova, a Professor at Université de Montréal, among other appointments. "We were motivated by a critical question: Could genetic factors underlie the association between WMH and cortical thinning, and might they also explain part of the observed risk for dementia? What we found was that yes, they can."
In this study, the researchers analyzed health and genetic data from 51,065 participants in various studies, with ages ranging from 19 to 100 years.
This effort showed that in every group analyzed, higher volumes of WMH were associated with reduced cortical thickness, noted co-corresponding study author Tomas Paus, a Professor at UdeM, among other appointments. This finding held true even when other factors were considered such as hypertension or diabetes.
The researchers noted that there was a particularly strong correlation between WMH and cortical thinning in an area known as the insula, which is a region of the brain that aids in the integration of cognitive, emotional, and sensory functions, noted Pausova.
The study also included a genome-wide association study (GWAS) that revealed twenty genetic loci that are associated with WMH-linked cortical thinning. Fifteen of these loci affect cortical genes, some of which are related to the maintenance of neuronal function.
The genetic patterns were also consistent in cells like astrocytes and oligodendrocytes that support neuronal health. This small blood vessel and axonal dysfunction could influence cortical atrophy. The scientists noted that this study emphasizes the significant influence of vascular health on dementia, and underlying genetic susceptibilities.
Sources: University of Montreal, Nature Communications