Conference Coverage
DTI Reveals Changes in Brain Connections in Early Alzheimer’s Disease
Changes in brain connections visible on MRI could represent an imaging biomarker of Alzheimer’s disease, according to a study presented at the meeting.
As many as five million Americans have Alzheimer’s disease, and this number is expected to increase to 14 million by 2050, according to the Centers for Disease Control and Prevention. Preventive treatments may be most effective before Alzheimer’s disease is diagnosed, such as when a person is experiencing mild cognitive impairment.
Previous efforts at early detection have focused on beta amyloid. For the current study, researchers looked at the brain’s structural connectome, a map of white matter tracts that carry signals between various areas of the brain.
“The structural connectome provides us with a way to characterize and measure these connections and how they change through disease or age,” said Jeffrey W. Prescott, MD, PhD, a radiology resident at Duke University Medical Center in Durham, North Carolina, and a coauthor of the study.
Dr. Prescott and colleagues analyzed data for 102 patients enrolled in a national study called the Alzheimer’s Disease Neuroimaging Initiative 2. The patients had undergone diffusion tensor imaging (DTI), which assesses the integrity of white matter tracts in the brain by measuring how easy it is for water to move along them. “Water prefers moving along the defined physical connections between regions in the brain, which makes DTI a great tool for evaluating the structural connectome,” said Dr. Prescott.
The researchers compared changes in the structural connectome with results from florbetapir PET imaging, a technique that measures the amount of beta amyloid plaque in the brain. The results showed a strong association between florbetapir uptake and decreases in the strength of the structural connectome in each of the five areas of the brain studied.
“This study ties together two of the major changes in the Alzheimer’s brain—structural tissue changes and pathologic amyloid plaque deposition—and suggests a promising role for DTI as a possible diagnostic adjunct,” said Dr. Prescott.
Based on these findings, DTI may have a role in assessing brain damage in early Alzheimer’s disease and in monitoring the effect of new therapies.
“Traditionally, Alzheimer’s disease is believed to exert its effects on thinking via damage to the brain’s gray matter, where most of the nerve cells are concentrated,” said Jeffrey R. Petrella, MD, Professor of Radiology at Duke University and senior author of the research. “This study suggests that amyloid deposition in the gray matter affects the associated white matter connections, which are essential for conducting messages across the billions of nerve cells in the brain, allowing for all aspects of mental function.”
“We suspect that as amyloid plaque load in the gray matter increases, the brain’s white matter starts to break down or malfunction and lose its ability to move water and neurochemicals efficiently,” added Dr. Prescott.
The researchers plan to continue studying this cohort of patients over time to gain a better understanding of how the disease evolves in individual patients. They also intend to incorporate functional imaging into their research to learn about how the relationship between function and structure changes with increasing amyloid burden.
Asymptomatic Atherosclerosis May Be Associated With Cognitive Impairment
A buildup of plaque in the body’s major arteries is associated with mild cognitive impairment, according to a study of approximately 2,000 adults conducted at the University of Texas (UT) Southwestern Medical Center.
“It is well established that plaque buildup in the arteries is a predictor of heart disease, but the relationship between atherosclerosis and brain health is less clear,” said Christopher D. Maroules, MD, a radiology resident at UT Southwestern Medical Center in Dallas. “Our findings suggest that atherosclerosis not only affects the heart, but also brain health.”
Researchers analyzed the test results of 1,903 participants (mean age, 44) in the Dallas Heart Study, a multiethnic population-based study of adults from Dallas County, Texas. The participants included men and women who had no symptoms of cardiovascular disease.
Study participants completed the Montreal Cognitive Assessment (MoCA), a 30-point standardized test for detecting mild cognitive impairment, and underwent MRI of the brain to measure white matter hyperintensity volume. Bright white spots known as high signal intensity areas on a brain MRI indicate abnormal changes within the white matter.
“Increased white matter hyperintensity volume is part of the normal aging process,” explained Dr. Maroules. “But excessive white matter hyperintensity volume is a marker for cognitive impairment.”
Study participants also underwent imaging exams to measure the buildup of plaque in the arteries in three distinct vascular areas of the body. They underwent MRI to measure wall thickness in the carotid arteries and in the abdominal aorta, and received CT to measure coronary artery calcium.