Efforts at early detection of Alzheimer's disease have focused on identifying beta amyloid plaque associated with the disease but other biomarkers may be identified using MRI, opening the field to a possible new diagnostic tool, according to a study released Monday.
The radiologists who presented the study at the Radiological Society of North America's annual meeting in Chicago used diffusion tensor imaging (DTI), an MRI method, to show that the brains of patients with early stage Alzheimer's disease have changes in white matter connections, such as fewer connections or connections that are less efficient. This can lead to forgetfulness and other signs of dementia.
After looking at 102 patients who had enrolled in the Alzheimer's Disease Neuroimaging Initiative and who had undergone DTI, the researchers found that the imaging method may help assess brain damage in early Alzheimer's patients. It also may help clinicians monitor the effect of therapies, they said. The initiative, formed in 2004, is working to develop biomarkers to use in clinical trials.
“It may be possible to use structural network topology as an imaging biomarker of Alzheimer's disease, and therefore as a target for therapy early in the course of (Alzheimer's disease),” the radiologists concluded in the study.
The presence of beta amyloid plaque in the brain is associated with Alzheimer's disease. Healthcare providers can use amyloid imaging to separate an Alzheimer's diagnosis from a diagnosis of another form of dementia. Prescott said amyloid imaging is the "best and most useful" screening tool so far but data has yet to prove its value and it's not yet reimbursed. The clinical exam remains the primary tool for diagnosis of Alzheimer's disease.
“This study ties together two of the major changes in the Alzheimer's brain—structural tissue changes and pathological amyloid plaque deposition—and suggests a promising role for DTI as a possible diagnostic adjunct,” Dr. Jeffrey Prescott, a radiology resident at Duke University Medical Center, said in a news release (PDF).
Providers are faced with several questions related to how best to diagnose patients with Alzheimer's disease. What tests work best? Are the tests accurate? And can an early diagnosis improve care for patients as the disease progresses?
The focus on using imaging to identify beta amyloid plaque has been fueled in part by the potential of treating those patients with beta amyloid inhibitors. But a pair of studies published early this year in the New England Journal of Medicine found that the inhibitors did not improve cognition in patients with mild to moderate Alzheimer's disease in Phase 3 clinical trials.
An estimated five million people in the U.S. had Alzheimer's disease in 2013, and that number is expected to grow to 14 million in the next 35 years.
Some clinicians have pushed for more discussion around the impact of lifestyle such as the need to reduce diabetes and other types of dietary or behavioral changes that can contribute to cognitive decline.
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