Do white matter changes have clinical significance in Alzheimer's disease?

Background: Although white matter changes visible with MRI are generally considered to result from ischemia, it has become clear that these changes also appear in patients with Alzheimer's disease (AD). However, their significance in AD is unknown.

Objective: We evaluated the clinical significance of white matter changes in AD.

Methods: Ninety-six AD patients (79.4 +/- 5.92 years old) and 48 age-matched control subjects (80.0 +/- 7.03 years old) participated in the study. Three neuroradiologists assessed the degree of periventricular hyperintensities (PVH) and deep white matter hyperintensities (DWMH) using a modified Fazekas' rating scale. We examined whether there was a difference in the severity and the histogram pattern of the white matter changes, or in vascular factors (hypertension, diabetes mellitus, and ischemic heart disease) between the two groups. We also analyzed the association between the severity of the white matter changes and the degree of dementia (MMSE score and disease duration).

Results: There were no differences in the vascular factors between AD and control subjects. The degree of PVH in AD was severe compared with that in the control subjects. In histograms of the number of subjects with each degree of PVH severity, the distribution of AD patients had peaks at both the low and intermediate degrees of PVH, while most of the controls had a low degree of PVH. There was no difference in the degree or the histogram pattern of DWMH between the two groups. The severity of white matter changes was not associated with severity of dementia in AD.

Conclusions: Although PVH might have several causative factors, and may have some clinical significance, the change itself does not contribute to the progression of AD.