Imaging Test

Typically, scientists look at the brain’s gray matter when investigating Alzheimer’s disease. A new study, however, finds that degenerating white matter in the brain could be an early indicator of the disease.

A study published in Radiology concludes that white matter plays an important role in how the disease strikes and progresses.

Alzheimer’s disease (AD) creates abnormal deposits of proteins that form amyloid plaques and tau tangles throughout the brain. It is also characterized by a loss of neurons, a process that causes brain tissue to shrink.

Alzheimers Biomarker

Dr. Massimo Filippi, who led the study, deployed diffusion tensor imaging (DTI) to examine white matter tracts in 53 patients with three types of Alzheimer’s: early-onset and two atypical types of Alzheimer’s called focal syndromes. DTI is a specialized MRI technique.

The scientists found that all of the patients had extensive damage to white matter and displayed regional gray matter damage.

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Their findings align with the theory that the disease’s pathology may travel along white matter fibers in different regions of the brain.

“In early-onset AD and atypical AD forms, white matter degeneration may be an early marker that precedes gray matter atrophy,” said Dr. Federica Agosta, Ph.D., the study’s co-author, in a statement. “DTI has the potential to assess the extensive disorganization of brain networks in focal AD even before overt cognitive deficits become apparent.”

Agosta said it is important to identify and diagnose patients with early onset and focal syndromes.

“Because there is not much structural damage in the early stages of focal Alzheimer's disease, there is a risk that patients may be misdiagnosed and excluded from clinical trials,” she added.

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More Work to Do

The idea of having a scan to see if you are developing Alzheimer’s disease sounds simple, but the technology is still beyond the horizon.

Changiz Geula, Ph.D., an Alzheimer’s disease researcher and professor from Northwestern University, said the study’s results provide a “tantalizing possibility” that imaging of white matter can differentiate early onset Alzheimer’s as well as atypical variants of the disease.

Before the test could be used clinically, however, he said the method must show it can distinguish Alzheimer’s subtypes from other forms of dementia.

“This issue is most relevant in relation to the atypical Alzheimer’s disease cases with language deficits, a type of dementia called primary progressive aphasia (PPA), which were included in the present study,” Geula said. “Only about 40 percent of PPA patients’ brains contain Alzheimer’s disease pathology. The rest show a number of other pathologies characteristic of other types of dementia.”

In order to be a specific biomarker of Alzheimer’s subtypes, the extent of white matter degeneration would have to be able to differentiate PPA with Alzheimer’s pathology from PPA cases without Alzheimer’s pathology.

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