Diffusion tensor imaging ‘should be routine’ in SVD assessment
medwireNews: Gait speed and microstructural brain damage may be the best indicators of mortality risk in patients with small vessel disease (SVD), say researchers.
The findings arise from an average 7.8 years of follow-up involving 503 participants of the Radboud University Nijmegen Diffusion Tensor and Magnetic Resonance Cohort (RUN DMC). The participants had SVD, were aged between 50 and 85 years, and 15.9% died during follow-up.
The model that best predicted mortality in the RUN DMC included age, gait speed, grey matter volume and the mean diffusivity of white matter; these factors together were 80% accurate for predicting mortality.
Each standard deviation (SD) increase in baseline grey matter volume was associated with a 25% reduction in mortality risk over the next 8 years, and each SD increase in the mean diffusivity of white matter, indicative of decreased microstructural integrity, was associated with a 53% increased mortality risk.
In an editorial accompanying the study, Wolf-Dieter Heiss (Max Planck Institute for Metabolism Research, Cologne, Germany) highlights the fact that these two imaging parameters predicted mortality, whereas traditional indices of SVD, such as lacunes and mircobleeds, were not predictive. This is in line with previous findings and suggests “that the connectivity in networks as assessed by diffusion tensor imaging is more important for outcome than the extent of primary structural lesions”, he says.
Both diffusivity and traditional magnetic resonance imaging markers should therefore be routinely assessed in SVD patients, he says.
“Because these changes of covert cerebrovascular disease may be manifested in clinically asymptomatic persons as early as the fifth decade of life, early detection of SVD is relevant for establishing the vital health status of these individuals and for developing and testing interventions for improving the potential risks for affected adults”, he writes in JAMA Neurology.
Besides the imaging markers, each 0.1 m/s reduction in gait speed was associated with a 13% increase in mortality risk, despite cognitive performance not being predictive.
Study author Frank-Erik de Leeuw (Radboud University Medical Center, Nijmegen, the Netherlands) and colleagues note that reduced gait probably reflects damage to multiple systems – not just the brain. Because the effects of SVD manifest most clearly in the brain, as cognitive impairment, “it could be that the association between cognitive performance and mortality is mediated by SVD”, they suggest.
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