Simple MRI score aids prediction of dementia in cerebral small vessel disease

Abstract

Objective: To determine whether a simple small vessel disease (SVD) score, which uses information available on rapid visual assessment of clinical MRI scans, predicts risk of cognitive decline and dementia, above that provided by simple clinical measures.

Methods: Three prospective longitudinal cohort studies (SCANS [St George's Cognition and Neuroimaging in Stroke], RUN DMC [Radboud University Nijmegen Diffusion Imaging and Magnetic Resonance Imaging Cohort], and the ASPS [Austrian Stroke Prevention Study]), which covered a range of SVD severity from mild and asymptomatic to severe and symptomatic, were included. In all studies, MRI was performed at baseline, cognitive tests repeated during follow-up, and progression to dementia recorded prospectively. Outcome measures were cognitive decline and onset of dementia during follow-up. We determined whether the SVD score predicted risk of cognitive decline and future dementia. We also determined whether using the score to select a group of patients with more severe disease would reduce sample sizes for clinical intervention trials.

Results: In a pooled analysis of all 3 cohorts, the score improved prediction of dementia (area under the curve [AUC], 0.85; 95% confidence interval [CI], 0.81-0.89) compared with that from clinical risk factors alone (AUC, 0.76; 95% CI, 0.71-0.81). Predictive performance was higher in patients with more severe SVD. Power calculations showed selecting patients with a higher score reduced sample sizes required for hypothetical clinical trials by 40%-66% depending on the outcome measure used.

Conclusions: A simple SVD score, easily obtainable from clinical MRI scans and therefore applicable in routine clinical practice, aided prediction of future dementia risk.

Figure 1. Receiver operating characteristic (ROC) curves illustrate the improved prediction of dementia when the simple MRI score is added to a model adjusted for age, sex, and education

Results are shown for a model without the MRI score (red line), after adding a simple MRI score (green line), and after adding an amended MRI score (blue line). p Value shows the statistical difference among ROC curves (blue: simple small vessel disease [SVD] score vs model without score; green: amended SVD score vs model without score).

Figure 2. Cognitive change plotted against simple small vessel disease (SVD) score for the 3 cognitive indices (upper panel, global cognition; middle panel, executive function; lower panel, processing speed) for the 3 cohorts (St George's Cognition and Neuroimaging in Stroke [SCANS], Radboud University Nijmegen Diffusion Imaging and Magnetic Resonance Imaging Cohort [RUN DMC], and Austrian Stroke Prevention Study [ASPS])

The slopes were used from a linear mixed effect analysis.