Pittsburgh compound-B PET white matter imaging and cognitive function in late multiple sclerosis

Background: There is growing interest in white matter (WM) imaging with positron emission tomography (PET). Objectives: We studied the association of cognitive function in late multiple sclerosis (MS) with cortical and WM Pittsburgh compound-B PET (PiB-PET) binding. Methods: In the population-based Mayo Clinic Study of Aging, 24 of 4869 participants had MS (12 underwent PiB-PET). Controls were age and sex matched (5:1). We used automated or semi-automated processing for quantitative image analyses and conditional logistic regression for group differences. Results: MS patients had lower memory (p=0.03) and language (p=0.02) performance; smaller thalamic volumes (p=0.003); and thinner temporal (p=0.001) and frontal (p=0.045) cortices on magnetic resonance imaging (MRI) than controls. There was no difference in global cortical PiB standardized uptake value ratios between MS and controls (p=0.35). PiB uptake was lower in areas of WM hyperintensities compared to normal-appearing white matter (NAWM) in MS (p=0.0002). Reduced PiB uptake in both the areas of WM hyperintensities (r=0.65; p=0.02) and NAWM (r=0.69; p=0.01) was associated with decreased visuospatial performance in MS. Conclusion: PiB uptake in the cortex in late MS is not different from normal age-matched controls. PiB uptake in the WM in late MS may be a marker of the large network structures' integrity such as those involved in visuospatial performance.