Brain magnets can detect hard-to-diagnose dementia

Transcranial magnetic stimulation – a non-invasive method of stimulating nerve cells within the brain by exposing them to targeted magnetic fields – is very much the current therapy du jour, with advocates claiming it can be used to treat depression and improve learning outcomes.

Now research published in the journal Neurology suggests it might also be a valuable diagnostic tool for distinguishing between Alzheimer’s disease and another, superficially similar, type of dementia.

Frontotemporal dementia, once thought to be rare, produces behavioural and cognitive changes very similar to those caused by Alzheimer’s, but has a different cause.

In the past, because those with the condition returned negative results to standard tests for Alzheimer’s, they were often thought to have a psychiatric rather than physical illness.

Today frontotemporal dementia is thought to account for as much as 15% of all dementia cases. Diagnosis, though, remains challenging. Invasive and painful lumbar punctures can improve the likelihood of identification but often the disease is only confirmed during autopsy.

However, researchers at the University of Brescia in Italy report that positioning a large electromagnetic coil against the scalp of patients can yield results that considerably improve the odds of identifying the condition, and doing so soon after onset.

The team, led by Barbara Borroni, performed transcranial magnetic stimulation (TMS) using the coil on a cohort of volunteers and measured the brain’s ability to conduct the resulting signals.

Patients with probable frontotemporal dementia were found to use significantly different neural pathways to those with suspected Alzheimer’s, or healthy controls.

The study involved 172 volunteers. The tests distinguished between the two forms of dementia with 90% accuracy – about the same level of precision achieved by lumbar punctures.

Borroni’s team is cautious in its findings, calling for more research before the method is declared effective and reliable.

The team acknowledge the sample size is too small to provide definitive results. Also, the work was not fully blind: the researchers were aware of which participants were healthy when they administered TMS, although they did not know which of the dementia patients were thought to have which condition.

Despite these shortcomings, however, Borroni expresses optimism about the findings. “If our results can be replicated with larger studies, this will be very exciting,” she says.

“Doctors might soon be able to quickly and easily diagnose frontotemporal dementia with this non-invasive procedure. This disease unfortunately can’t be cured, but it can be managed – especially if it is caught early.”