Signs of Parkinson’s disease can be detected 20-30 years before symptoms appear using a known biomarker, called F-AV-133, and positron emission tomography (PET) scans, according to a new study from researchers at Austin Health and the Florey Institute at the University of Melbourne. This work opens the door to screening programs and preventative treatments long before irreversible damage is done. The study is out this week in Neurology.
“Parkinson’s disease is very hard to diagnose until symptoms are obvious, by which time up to 85 percent of the brain’s neurons that control motor coordination have been destroyed. At that point, many treatments are likely to be ineffective,” said Kevin Barnham, PhD, a professor at Florey and one of the paper’s authors.
Barnham added that Parkinson’s disease is often thought of as an illness of old age, when in fact it starts in midlife and can go undetected for decades. “Our long-term goal is to find a way to detect the disease much earlier and treat people before the damage is done.”
According to The Parkinson’s Foundation, an estimated 10 million people worldwide have the disease. The diagnosis is made based on an individual’s history, symptoms, and physical exam are used to make the diagnosis. There is not a specific lab or imaging test that can diagnose Parkinson’s.
In this study, Florey professor Chris Rowe, MD, and his team at Austin Health scanned 26 patients with Parkinson’s disease, a control group of 12 people, and 11 people with Rapid Eye Movement sleep behavior disorder (RBD), which is a strong indicator of the disease. Patients with RBD shout or thrash around, sometimes violently, in their sleep while acting out vivid and unpleasant dreams. It is caused by a lack of muscle atonia (sleep paralysis) and 90 percent of people with RBD will develop a parkinsonian condition.
Each person undertook two PET scans two years apart. Regions of interest included caudate, anterior and posterior putamen. At the time of scanning participants underwent clinical evaluation including UPDRS MOTOR test, Sniffin’ Sticks, and Hospital Anxiety and Depression Score.
The team found no significant changes in clinical symptoms in any of the participants according to currently available assessments for Parkinson’s disease. By contrast, the PET scans showed “significant neuronal loss” in three key regions of the brain in individuals with the disease, suggesting F-AV-133 is a more sensitive means of monitoring neurodegeneration than what is now available.
Using mathematical modeling they calculated:
- An approximate total of 33 years’ slow neuronal loss in Parkinson’s disease.
- This loss, they estimated, occurs for about 10.5 years before the disease is detectable on a PET scan.
- Once a PET scan is able to detect the disease, it will be a further six and a half years before the onset of motor symptoms.
- After onset of physical symptoms, there are about a further three years until clinical diagnosis is confirmed.
- This equates, they estimated, to neuronal loss occurring for about 22.5 years before clinical symptoms are sufficient for diagnosis.
Barnham said the findings open pathways to developing screening protocols for diagnosing and treating Parkinson’s disease up to 10 years earlier than is currently possible. It could also assist in identifying patients for clinical trials.