Attention processing speed impairment in early dementia with Lewy bodies correlates with white matter damage on volumetric and diffusion tensor imaging

Background Attentional deficit is a prominent and distinguishing neuropsychological feature of Dementia with Lewy Bodies (DLB) since the prodromal stages. Our group recently highlighted, using voxel based morphometry (VBM), the importance of the basal ganglia grey matter (GM) integrity for attention processing speed, however, one can hypothesize that white matter (WM) would also be affected. Accordingly, this study aimed at investigating, in early DLB patients, the relationship between impaired attention processing speed and white matter changes using WM‐VBM and diffusion tensor imaging (DTI). Method Seventy‐three prodromal to moderate DLB patients (mean MMSE = 26.4) and thirty healthy elderly subjects (mean MMSE = 28.9), matched in terms of age and educational level, were selected to participate in the study. The Trail Making Test A (TMTA) was used to assess attention processing speed. Behavioral performances were compared between patients and control subjects. Three‐dimensional (3D) MRI and diffusion tensor images (DTI) were acquired and correlational analyses were performed in the patient group using GM‐ and WM‐VBM, fractional anisotropy (FA) and mean diffusivity (MD) DTI. Result As expected, DLB patients took significantly more time to achieve completion of the TMTA in comparison to control subjects (p = .004), indicating an impairment in speed of processing. Correlational analyses using VBM revealed negative GM correlations in the basal ganglia bilaterally (p < .001), and negative WM correlations in a bilateral but left‐predominant cluster including mainly the corpus callosum and the anterior cingulate region and a smaller cluster in the right anterior cingulum (p < .05 FDR corrected). Using DTI in correlation with TMTA scores (p < .05 FDR corrected), we found reduced FA in bilateral frontal and posterior regions, and increased MD in widespread lateral and medial anterior and posterior regions. Conclusion WM‐VBM analysis revealed the involvement of the anterior corpus callosum and cingulum in processing speed, which could indicate a disruption of the loops connecting striatal regions and the prefrontal cortex. Changes in both FA and MD were also found: their distribution suggest that attention processing speed might be particularly dependent on the integrity of white matter connections throughout the brain.