MRI brain scans may be more effective than common clinical tests at predicting a person’s risk of developing 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.
But it remains elusive: the disease cannot technically be diagnosed during life (only in an autopsy) and scientists haven’t been able to say for certain what a brain destined for Alzheimer’s looks like.
Currently, doctors are able to spot about 70 percent of cases early using questionnaires to measure cognition, and genetic tests for the gene APOE4, which is linked to 50 percent of Alzheimer’s cases (but is also detected in healthy people).
However, a new study, published today by a team at Washington University School of Medicine, found tell-tale symptoms that appeared on up to 95 percent of MRI scans of future Alzheimer’s patients before the disease set in.
The small study of 61 patients at Washington University suggests a technique that, if successful, would be a better alternative to the current questionnaire screening method
If the finding can be replicated in a bigger group (this study involved 61 people) it could pave the way to the first ever concrete screening technique for Alzheimer’s, which is infecting more and more people at an alarming rate.
Though 70 percent sounds like a fairly high accuracy rate for the current tests, Alzheimer’s is becoming more and more common. Missing 30 percent of cases is a huge margin of error in the grand scheme of things.
The new MRI scans conducted at Washingotn, using diffusion tensor imaging (DTI) to assess the condition of the brain’s white matter, were found to be between 89 and 95 percent accurate.
‘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,’ the study’s lead author Dr Cyrus Raji, assistant professor of radiology at the school’s Mallinckrodt Institute of Radiology, said.
‘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 percent 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 percent.’
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 percent 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.