Peripheral (deep) but not periventricular MRI white matter hyperintensities are increased in clinical vascular dementia compared to Alzheimer's disease

Abstract

Background and purposeVascular dementia (VAD) is a complex diagnosis at times difficult to distinguish from Alzheimer's disease (AD). MRI scans often show white matter hyperintensities (WMH) in both conditions. WMH increase with age, and both VAD and AD are associated with aging, thus presenting an attribution conundrum. In this study, we sought to show whether the amount of WMH in deep white matter (dWMH), versus periventricular white matter (PVH), would aid in the distinction between VAD and AD, independent of age.MethodsBlinded semiquantitative ratings of WMH validated by objective quantitation of WMH volume from standardized MRI image acquisitions. PVH and dWMH were rated separately and independently by two different examiners using the Scheltens scale. Receiver operator characteristic (ROC) curves were generated using logistic regression to assess classification of VAD (13 patients) versus AD (129 patients). Clinical diagnoses were made in a specialty memory disorders clinic.ResultsUsing PVH rating alone, overall classification (area under the ROC curve, AUC) was 75%, due only to the difference in age between VAD and AD patients in our study and not PVH. In contrast, dWMH rating produced 86% classification accuracy with no independent contribution from age. A global Longstreth rating that combines dWMH and PVH gave an 88% AUC.ConclusionsIncreased dWMH indicate a higher likelihood of VAD versus AD. Assessment of dWMH on MRI scans using Scheltens and Longstreth scales may aid the clinician in distinguishing the two conditions.

White Matter Hyperintensity Associations with Cerebral Blood Flow in Elderly Subjects Stratified by Cerebrovascular Risk

“…We divided WMH into dWMH and pWMH for several reasons[10, 38–42]. Firstly, the white matter tracts adjacent to the ventricles encompassed by pWMH are limbic (cingulum) and motor (corticospinal and related tracts), whereas dWMH are more likely to involve long association tracts and thus long-range inter-regional connectivity.…”

“…Firstly, the white matter tracts adjacent to the ventricles encompassed by pWMH are limbic (cingulum) and motor (corticospinal and related tracts), whereas dWMH are more likely to involve long association tracts and thus long-range inter-regional connectivity. The possibility that clinical correlates of dWMH and pWMH may be different is also supported by the association of dWMH but not pWMH with vascular dementia [10, 43]. Finally, the small-vessel circulation in white matter may be different between deep and periventricular zones, with a greater vulnerability of the periventricular region to large- vessel disease [44].…”

“…WM was modeled as two separate tissue classes to represent variations due to WM intensities [10]. The International Consortium for Brain Mapping (ICBM) atlas reference was registered to the segmentation template, and atlas regions combined to create masks representing the frontal, temporal, parietal and occipital brain regions for both GM (Figure 2B) and WM (Figure 2C).…”

“…Manual editing of extraneous pixels due to pulsation and flow artifacts was needed occasionally, resulting in the final WMH image (Figure 3H), quantitated by calculating total voxels and total WMH voxel volume [10]. …”

Clinically silent Alzheimer's and vascular pathologies influence brain networks supporting executive function in healthy older adults

“…WMH volumes were computed in older adults using an overall framework employed in our recent work (Smith et al, 2016). The series of steps included field correction using the N3 algorithm, co-registration of the two T1-weighted images using FSL’s Linear Registration Tool (FLIRT), T1 image averaging, skull-stripping and segmenting using Freesurfer.…”