麻豆传媒

People destined to suffer the misery of memory loss and senility could learn their fate in advance, thanks to a new technique involving brain scanning. But with no tried and tested cure yet available, would anyone really want to know? There are also fears the results could be used by employers or insurance companies to discriminate against people affected.

Photo: K Kasmauski/Katz

At the moment, most neurological diseases cannot be diagnosed until behavioural problems start. But Mony de Leon of the New York University School of Medicine and his colleagues have found that several years before the symptoms of Alzheimer鈥檚 set in, part of the brain starts using less fuel.

The researchers studied 48 apparently healthy volunteers in their 60s, 70s and 80s. At the start of the study all the volunteers achieved normal scores on a number of cognitive tests, but when tested again three years later, 13 did considerably worse. One was diagnosed with Alzheimer鈥檚 disease, while the remaining 12 were diagnosed with 鈥渕ild cognitive impairment鈥� or MCI.

All the volunteers had also been given a PET scan, which can show where glucose is being metabolised in the brain. To find out if anything in the scans could have predicted cognitive decline, the researchers selected 13 controls matched for age, sex, education level and genetic risk of Alzheimer鈥檚 from the people who were still healthy.

More accessible

Leon鈥檚 team looked at several brain areas known to be involved in memory 鈥� and in Alzheimer鈥檚 鈥� and found one important difference between the group suffering memory loss and the controls. The entorhinal cortex used substantially less glucose in those whose memory subsequently deteriorated. This difference, the researchers say, can predict future memory loss up to three years in advance. They report their findings in a future issue of Proceedings of the National Academy of Sciences.

PET scans are too expensive and invasive for routine screening, so are only useful for people already at high risk of Alzheimer鈥檚. But attempts to make the approach more accessible are already under way.

Cognitive computer scientist Richard Granger of the University of California, Irvine, and his team have developed a portable head cap which carries electrodes for analysing electrical activity in the brain. The test takes only 12 minutes, and can pick out people who already have Alzheimer鈥檚, MCI or depression with up to 98 per cent accuracy. Granger is now using the test to look for patterns that are shared by the brains of people who go on to suffer from particular diseases.

Routine alerts

It remains to be seen whether the technique can predict these conditions before clinical symptoms occur, and if so how early. 鈥淭hat鈥檚 exactly what we鈥檙e trying to find out now,鈥� says Granger.

Gary Small, a neuroscientist at the University of California, Los Angeles, believes that brain scans in some form could eventually be used routinely to alert vulnerable people well in advance 鈥� perhaps decades ahead. Granger believes that such early diagnosis can do only good. If people have a disease then they will want to know about it as early as possible, he says.

鈥淭here are always risks for abuse,鈥� says Small, 鈥渂ut there are also tremendous benefits.鈥� People who are told they will have Alzheimer鈥檚 could decide whether to take preventive measures, he says. Antioxidants such as vitamin E, anti-inflammatory drugs and cholinesterase inhibitors may all slow the disease down, but it鈥檚 not clear by how much.