Reader Response: Simple MRI Score Aids Prediction of Dementia in Cerebral Small Vessel Disease

I read with interest the article by Amin Al Olama et al.¹ that used a simple small vessel disease (SVD) score (0–3) from rapid visual assessment of clinical MRI scans to predict the risk of cognitive decline and dementia in a pooled analysis of 3 cohorts. They found that a simple SVD score could be more valuable to predict future dementia risk.¹ This work would be greatly helpful for our clinicians to measure the SVD cases who will progress to dementia just by using simple and available routine clinical MRI scans. However, there are still some issues that should be addressed. First, as one of the most important biomarkers of SVD, enlarged perivascular spaces (ePVS) were not included in this simple SVD score, which may be due to the finding that ePVS was not associated with cognitive dysfunction in a recent meta-analysis of 5 cross-sectional studies.² However, whether ePVS contributes to cognitive decline should be further confirmed in longitudinal studies. As a result, it should be with caution that a conclusion be made that ePVS is not associated with cognitive decline with the evidence from cross-sectional studies.³ Second, there were great heterogeneities in the above 3 different studies by using a battery of neuropsychological tests such as global cognition, executive function, and processing speed.² Third, different study populations, different follow-up periods, different dementia diagnostic criteria, the heterogeneity of SVD lesions, and large variability in clinical symptoms among patients with SVD all contributed to some selection bias or heterogeneities. As a result, as a global rather than a focal disease, the combined structural and functional connectivities to explore how network disruption by SVD can lead to cognitive deficits and its underlying compensatory mechanisms could be more convincing and promising.⁴ Network disruption may have a central role in the pathogenesis of cognitive decline and dementia in SVD.^5,6