MRI scans ‘predict which people will develop Alzheimer’s’

MRI brain scans perform better than common clinical tests at predicting which people will develop Alzheimer’s disease, according to a new study.

Alzheimer’s disease is a progressive, irreversible brain disorder that destroys memory and thinking skills – and the number of people being diagnosed is soaring.

Experts say that common predictive models such as questionnaires used to measure cognition and tests for APOE4 , a gene variant associated with a higher risk of Alzheimer’s, have limitations.

The accuracy rates of about 70 per cent fail to identify many people who go on to develop the disease.

But MRI scans of the brain using diffusion tensor imaging (DTI), which assess the condition of the brain’s white matter, were found to be between 89 and 95 per cent accurate.

Study lead author Dr Cyrus Raji, Assistant Professor of radiology at the Mallinckrodt Institute of Radiology at Washington University School of Medicine in the US, said: “Alzheimer’s disease is the most common cause of dementia in the world and is expected to increase globally, and especially in the US, as the population gets older.

“As we develop new drug therapies and study them in trials, we need to identify individuals who will benefit from these drugs earlier in the course of the disease.

“With DTI you look at the movement of water molecules along white matter tracts, the telephone cables of brain.

“When these tracts are not well connected, cognitive problems can result.”

He said DTI provides different measures of white matter integrity, including fractional anisotropy (FA), a measure of how well water molecules move along white matter tracts.

A higher FA value indicates that water is moving in a more orderly fashion along the tracts, while a lower value means that the tracts are likely damaged.

For the new study, Dr. Raji and his colleagues set out to quantify differences in DTI in people who decline from normal cognition or mild cognitive impairment to Alzheimer’s dementia compared to controls who do not develop dementia.

They performed brain DTI scans on 61 people drawn from the Alzheimer’s Disease Neuroimaging Initiative, a major study focusing on the progression of the disease.

About half of the patients went on to develop Alzheimer’s, and DTI identified “quantifiable differences” in the brains of those patients.

People who developed the disease had lower FA compared with those who didn’t, suggesting white matter damage. They also had statistically significant reductions in certain frontal white matter tracts.

Dr Raji said: “DTI performed very well compared to other clinical measures.

“Using FA values and other associated global metrics of white matter integrity, we were able to achieve 89 per cent accuracy in predicting who would go onto develop Alzheimer’s disease. The Mini-mental State Examination and APOE4 gene testing have accuracy rates of about 70 to 71 per cent.”

The researchers conducted a more detailed analysis of the white matter tracts in about 40 of the study participants.

Dr Raji said that, among those patients, the technique achieved 95 per cent accuracy.

He said many people already receive MRI as part of their care, so DTI could add “significant value” to the exam without substantially increasing the costs.

Dr Raji said MRI measures of white matter integrity could speed interventions that slow the course of the disease or even delay its onset.

He added: “Research shows that Alzheimer’s disease risk can be reduced by addressing modifiable risk factors like obesity and diabetes.

“With early detection, we can enact lifestyle interventions and enlist volunteers into drug trials earlier.”

The findings are due to be presented at the annual meeting of the Radiological Society of North America (RSNA) in Chicago next week.

By Stephen Beech

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