Testing tears could lead to cheap and effective Parkinson's disease screening

Parkinson’s patients’ tears had more than five times the level of abnormal molecule which forms nerve damaging clumps

MRI scan of a Parkinson’s patient (Getty)

A few shed tears could open up a cheap way to screen patients for Parkinson’s disease, allowing earlier diagnosis and, potentially, treatment that can delay the disease.

Researchers analysing the tears of Parkinson’s patients and non-affected adults found that patients with the disease had five times the level of alpha-synuclein, the protein molecule that forms toxic clumps and causes nerve damage, than the healthy patients.

“We believe our research is the first to show that tears may be a reliable, inexpensive and non-invasive biological marker of Parkinson’s disease,” said the study’s author, Dr Mark Lew, from the Keck School of Medicine at the University of Southern California.

“And because the Parkinson’s disease process can begin years or decades before symptoms appear, a biological marker like this could be useful in diagnosing, or even treating, the disease earlier.”

The findings from an early human trial were presented at a conference of the American Academy of Neurology today.

Because Parkinson’s affects nerve signals around the body and not just in the brain, Dr Lew’s team predicted that the abnormal protein molecules linked with it’s progression would be found outside the brain as well.

The researchers recruited 55 people with Parkinson’s, and 27 people from a similar mix of ages and genders without the disease, and compared tear samples for differing levels of the protein.

They found levels of alpha-synuclein in a healthy, non-clumped form were lower in Parkinson’s patients’ tears.

However, they had significantly higher levels of the unhealthy form of the molecule, oligomeric alpha-synuclein – 1.45 nanograms per milligram of tear proteins, compared to 0.27 nanograms in healthy patients.

These abnormal protein clumps interfere with nerve signals and are a key factor in the nerve damage that marks out the progression of Parkinson’s disease.

“Knowing that something as simple as tears could help neurologists differentiate between people who have Parkinson’s disease and those who don’t in a non-invasive manner is exciting,” said Dr Lew.

Detecting Parkinson’s disease from bodily secretions isn’t entirely new.

Manchester academics are studying retired nurse Joy Milne’s peculiar ability to smell Parkinson’s and identify sufferers with remarkable accuracy.