Unexpected findings
Mean WMH volume was significantly higher in participants with FTD than in participants with Alzheimer’s disease and in healthy controls (mean, 0.76 mL, 0.40 mL, and 0.12 mL respectively). These larger volumes contributed to greater disease severity and cortical atrophy. Moreover, disease severity was “found to be a strong predictor of WMH volume in FTD,” the authors stated. Among patients with FTD, WMH volumes did not differ significantly with regard to genetic mutation status or presence of strong family history.
After controlling for age, vascular risk did not significantly predict WMH volume in the FTD group (P = .16); however, that did not hold true in the Alzheimer’s disease group.
Increased WMH were associated with anterior brain regions in FTD and with posterior brain regions in Alzheimer’s disease. In both disorders, higher WMH volume in the corpus callosum was associated with poorer cognitive performance in the domain of attention.
“The spatial distribution of WMH mirrored patterns of brain atrophy in FTD and Alzheimer’s disease, was partially independent of cortical degeneration, and was correlated with cognitive deficits,” said Dr. Landin-Romero.
The findings were not what he and his research colleagues expected. “We were expecting that the amounts of WMH would be similar in FTD and Alzheimer’s disease, but we actually found higher levels in participants with FTD,” he said. Additionally, he anticipated that patients with either FTD or Alzheimer’s disease who had more severe disease would have more WMH, but that finding only held true for people with FTD.
“In sum, our findings show that WMH are a core feature of FTD and Alzheimer’s disease that can contribute to cognitive problems, and not simply as a marker of vascular disease,” said Dr. Landin-Romero.
Major research contribution
Commenting on the study, Jordi Matias-Guiu, PhD, MD, of the department of neurology, Hospital Clinico, San Carlos, Spain, considers the study to be a “great contribution to the field.” Dr. Matias-Guiu, who was not involved with the study, said that WMH “do not necessarily mean vascular pathology, and atrophy may partially explain these abnormalities and should be taken into account in the interpretation of brain MRI.
“WMH are present in both Alzheimer’s disease and FTD and are relevant to cognitive deficits found in these disorders,” he added.
The study was funded by grants from the National Health and Medical Research Council of Australia, the Dementia Research Team, and the ARC Center of Excellence in Cognition and Its Disorders. Dr. Landin-Romero is supported by the Appenzeller Neuroscience Fellowship in Alzheimer’s Disease and the ARC Center of Excellence in Cognition and Its Disorders Memory Program. The other authors’ disclosures are listed on the original article. Dr. Matias-Guiu reports no relevant financial relationships.
A version of this article first appeared on Medscape.com.