Tears as a New Diagnostic Tool for Parkinson's?

Go ahead and cry... a few tears may be the newest way to diagnose Parkinson's disease (PD). That's right, it seems that proteins found in tears of people with PD have significantly higher levels of oligomeric alpha synuclein proteins than people unaffected by PD. Have you heard about the woman in England who could smell Parkinson's in her husband and others before they were diagnosed? Joy Milne was able to smell a distinct change in odor due to sweat secretions in people with PD. Studies in the UK went on to confirm the accuracy of these smell tests and they continue to study the changes in sweat secretions as a predictor of Parkinson's disease.

Capturing tears

Dr. Mark Lew from the Keck School of Medicine at the University of Southern California (USC) announced preliminary findings from early human trials that will be presented at the American Academy of Neurology.1 A small-scale study evaluated 55 people with Parkinson's, and 27 who were matched for age and gender that did not have the disease. Tears are collected in a process called the Schrimer Test by using a special piece of paper placed beneath the eyes to catch the moisture. Tear samples were then evaluated for levels of particular alpha synuclein proteins.

The body produces different kinds of alpha synuclein proteins. In Parkinson's disease, oligomeric alpha synuclein proteins clump together causing damage to neurons in the substantia nigra. Studies revealed nearly a six-fold increase in oligomeric alpha synculein in Parkinson's patients than in the control population which had higher levels of the monomeric form.2

Tears may tell more than joy or sadness

New studies will evaluate whether analyzing tears for specific proteins will enable researchers to not only diagnose people who are already experiencing symptoms of PD but also to identify people before they manifest the disease, or in the earliest stages. Larger scale studies will explore the differences between PD and non-PD sample populations. The variable amounts and types of alpha synuclein will be measured.

The differences in tear proteins could be due to the presence of Parkinson's disease, or it is also possible that glands that secrete tears also produce different kinds of proteins. This is an area requiring further scientific study. The presence of specific alpha synculein proteins in tears could turn out to be a bio-marker for PD where screening is accessible to all, being both inexpensive and non-invasive, according to Dr. Lew.3

Scientists have known that Parkinson's takes years to develop and has many idiosyncratic precursors that may appear years before the motor symptoms develop. Examples include a decreased sense of smell, difficulty sleeping, and depression.4

The team at USC sought to investigate whether affected nerve signals in PD could be found outside the brain. Since the condition is progressive and affects the entire body, the thought was that abnormal proteins might also be present beyond the brain.

Screening tears

Many advances in science have led to routine screenings in other areas of medicine like pregnancy and TB. If doctors can diagnose through a routine tear analysis, it may help identify who is likely to develop PD. That would enable the initiation of care and treatment before the onset of more advanced disease, as treatments and hopefully cures are found. There are medications in the pipeline which are thought to be disease slowing, so early identification could improve the efficacy of available interventions.

Larger scale studies are ongoing and along with future research will examine the influence of gender, age of onset, disease stage, and other factors. Research may also uncover information that has the potential to differentiate Parkinson's from other conditions that resemble PD.

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