Could the shape of white matter hyperintensities (WMHs) on brain magnetic resonance imaging (MRI) be a viable marker for predicting cognitive decline in older adults?
In a recent study, published in Neurobiology of Aging, researchers reviewed data from MRI scans and neuropsychological testing to determine the potential prognostic impact of irregular WMH shape upon executive function, memory, and processing speed domains in 2,493 community-dwelling older adults (mean age of 74.6 and body mass index of 27.2 kg/m3).
The study authors found that irregular shape of periventricular/confluent WMH on MRI scans was associated with cognitive decline in executive function, memory, and processing speed domains over a 5.2-year period.
For associations with cognitive decline in the memory domain, the study authors noted a higher fractal dimension (-0.07) and concavity index (-0.09) as well as lower convexity (-0.07) and lower solidity (-0.04) with periventricular/confluent WMH shape irregularity.
For cognitive decline with executive function, the researchers pointed out irregularity in periventricular/confluent WMH shape in the form of lower convexity (-0.04) as well as higher fractal impression (-0.04) and concavity index (-0.04). The study authors said those patients with cognitive decline in processing speed had lower solidity (-0.04) and convexity (-0.06) along with higher fractal dimension (-0.06) and concavity index (-0.08) with the irregular shape of periventricular WMH.
“Our study showed that WMH shape markers are associated with decline in individual cognitive domains over time. As these associations were largely independent of WMH volume, this suggests that WMH shape conveys additional information about WMHs, which is not captured by WMH volume alone,”wrote Jasmin Annica Kuhn-Keller, Ph.D., who is affiliated with the Department of Radiology at the Leiden University Medical Center in Leiden, the Netherlands, and colleagues.
Three Key Takeaways
1. WMH shape may help predicts cognitive decline. Irregular shapes of periventricular/confluent white matter hyperintensities (WMHs) on brain MRI are significantly associated with decline in executive function, memory, and processing speed over a 5.2-year period independent of WMH volume.
2. Specific shape markers matter with periventricular/confluent WMH. Cognitive decline appears to be correlated with specific WMH shape features, such as higher fractal dimension and concavity index, and lower convexity, suggesting these metrics may be useful in early identification of at-risk individuals.
3. Periventricular vs. deep WMH. While the shape of periventricular/confluent WMHs was linked to cognitive decline. the study authors found no significant association with deep WMH shape. The researchers added that more extensive changes in the regions of long associating fibers with subcortical nuclei and other more distant brain regions "may have more severe consequences" in contrast to the punctual changes one may detect in deep white matter regions.
The researchers also noted no associations between deep WMH shape and cognitive decline across the aforementioned domains on brain MRI.
“While deep WMH are often found in regions of short-looped U-fibers connecting different cortical regions, periventricular WMH largely involve regions of long associating fibers with subcortical nuclei and other more distant brain regions,” added Kuhn-Keller, Ph.D., and colleagues. “Therefore, the often more extensive changes in these long fiber regions may have more severe consequences, compared to punctual changes in deep white matter regions.”
(Editor’s note: For related content, see “What MRI-Derived Data and Other Factors Reveal About White Matter Hyperintensity in Former Football Players,” “Study Links PTSD to Higher Carotid Atherosclerosis and White Matter Hyperintensity in Midlife Women” and “New MRI Research Explores Links Between Waist-to-Hip Ratio and Memory in Aging.”)
In regard to study limitations, the authors noted the use of 1.5 T MRI scanners for the study, conceding that more current studies utilize 3.0 T MRI systems. The researchers acknowledged the time interval between the two visits for patients was not considered when calculating cognitive change in the cohort. The study authors also conceded that those who experience the most cognitive decline over time have a greater likelihood of being lost to follow-up.
