Common clinical tests are no match for MRI brain exams when it comes to predicting which patients will develop Alzheimer’s disease.
That’s among the findings of a study that will be presented at the annual meeting of the Radiological Society of North America, running from November 25 to 30 in Chicago.
According to researchers, common predictive models used to measure cognition and tests for the APOE4 gene variant—associated with higher risk of Alzheimer’s—have limitations as the accuracy of predictions only hit about the 70 percent mark.
However, MRI brain exams using diffusion tensor imaging (DTI) are showing promise for analysis of dementia as these exams assess the condition of the white matter in the brain.
“With DTI, you look at the movement of water molecules along white matter tracts—the telephone cables of the brain,” explains study lead author Cyrus Raji, MD, assistant professor of radiology at the Mallinckrodt Institute of Radiology at Washington University School of Medicine in St. Louis. “When these tracts are not well-connected, cognitive problems can result.”
Raji and colleagues quantified differences in DTI in people who decline from normal cognition or mild cognitive impairment to Alzheimer’s dementia compared to control groups of people who do not develop dementia. They also performed brain DTI exams on 61 people drawn from the Alzheimer’s Disease Neuroimaging Initiative, a major multi-site study.
About half of the patients developed the disease, and DTI exams then identified quantifiable differences in the brains of these subjects. People who developed the disease had lower levels of fractional anisotropy (FA), indicating that water was moving along white matter tracts that were likely damaged. They also had significant reductions in certain frontal white matter tracts.
DTI performed well compared to other clinical measures, according to Raji and the researchers achieved 89 percent accuracy in predicting development of Alzheimer’s, compared with other examinations that had accuracy of about 70 percent.
Researchers then conducted a more detailed analysis in about 40 study patients and among them the accuracy rate rose to 95 percent.
Importantly, MRI measures of white matter integrity could speed interventions that slow the course of the disease or even delay its onset, researchers contend.
“Research shows that Alzheimer’s disease risk can be reduced by addressing modifiable risk factors like obesity and diabetes,” Raji says. “With early detection, we can enact lifestyle interventions and enlist volunteers into drug trials earlier.”