Scientists now think they can detect dementia before the symptoms appear by using a special type of MRI brain scan technique.
The new test — which uses arterial spin labelling — relies on measuring the blood flow in a certain portion of the brain.
The test is sorely needed because early diagnosis of dementia is very important to effective therapies.
The number of people worldwide affected by dementia is currently at over 35 million, and those numbers are expected to double over the next 15 years.
The study which supports the use of this new test included 148 elderly people, around half of whom went on to develop signs of dementia over almost two years (Xekardaki et al., 2014).
Amongst those who later deteriorated, there was reduced blood flow in certain key areas of the brain, as measured at the start of the research.
In particular, reduced flow (or perfusion) was seen in the posterior cingulate cortex, an area in the middle of the brain which is active when our minds are not concentrating on anything specific.
Dr. Sven Haller, one of the study’s authors, said:
“There is a known close link between neural activity and brain perfusion in the posterior cingulate cortex.
Less perfusion indicates decreased neural activity.”
The reason that some people do not notice any symptoms of dementia, despite reduced flow, is that other areas of the brain are able to take up the slack.
The brain has a remarkable ability to recruit its cognitive reserves to make up for deficits caused by age or injury, but only up to a point.
Eventually the cognitive reserves are exhausted and the patient begins to notice some of the classic signs of dementia, like memory loss.
The test of blood flow in this area of the brain may prove a cheap and effective way of spotting these changes before the symptoms become obvious.
Currently PET scans are used to try and spot early signs of dementia, but these expose patients to radiation and are not as easy to administer.