Disruptions in brain networks emerge in patients with early Alzheimer’s disease at about the same time as chemical markers of the disease appear in the spinal fluid, according to a new study.
While two chemical markers in the spinal fluid are regarded as reliable indicators of early Alzheimer’s, the new study is among the first to show that scans of brain networks may be an equally effective and less invasive way to detect early disease, according to researchers at Washington University School of Medicine in St. Louis.
Diagnosing Alzheimer’s early is a top priority for physicians, many of whom believe that treating patients long before dementia starts greatly improves the chances of success, the researchers noted.
“Tracking damage to these brain networks may also help us formulate a more detailed understanding of what happens to the brain before the onset of dementia,” said senior author Beau Ances, M.D., Ph.D., and an associate professor of neurology and of biomedical engineering.
The research team studied 207 cognitively normal volunteers at the Charles F. and Joanne Knight Alzheimer’s Disease Research Center at Washington University. Over several years, spinal fluids from the volunteers were analyzed for two markers of early Alzheimer’s: changes in amyloid beta, the principal ingredient of Alzheimer’s brain plaques, and in tau protein, a structural component of nerve cells.
The volunteers were also scanned repeatedly using resting state functional magnetic resonance imaging (fMRI). This scan tracks the rise and fall of blood flow in different regions of the brain as patients rest in the scanner.
Scientists use the data to assess the integrity of the default mode network, a set of connections between different brain regions that becomes active when the mind is at rest.
Earlier studies by Ances and other researchers have shown that Alzheimer’s damages connections in the default mode network and other brain networks.
The new study revealed that this damage is detectable at about the same time that amyloid beta levels begin to rise and tau levels start to drop in spinal fluid.
The part of the default mode network most harmed by the onset of Alzheimer’s disease was the connection between two brain areas associated with memory, the posterior cingulate and medial temporal regions, the researchers discovered.