Changes in the brain that can be seen years before the physical symptoms of Parkinson's disease may act as a warning sign for the disease, say researchers.
It is believed that about 145,000 people in the UK are living with Parkinson's disease, a neurological condition that can lead to mobility problems, including slowness and tremors, as well as other symptoms such as memory difficulties. There are treatments to help control the symptoms, but so far the disease can not be delayed or cured.
The researchers, based at King's College London, say the latest findings may lead to new ways of identifying people who can develop Parkinson's; the findings could also confirm diagnoses, monitor disease progression, and aid in the development and testing of drugs. These developments may be a bit off, some scientists have said.
Most of the time, Parkinson's seems to have no known cause, so people affected by the disease are not studied before the symptoms appear.
But studies of King's College-related genetic mutations that make the development of Parkinson's disease more likely can point to warning signs.
Marios Politis, professor and lead author of the research, said: "If you carry the gene [SNCA] this means that it is almost certain that you will develop Parkinson's in the course of your life. "
It was believed that a genetic mutation involving the SNCA gene had arisen in villages in the Peloponnese, Greece.. But Politis said that the carriers are rare. "I do not think there are more than 100 [people who are known to have it]," he said.
Writing in the journal Lancet Neurology, Politis and his colleagues described how they brought 10 individuals with this genetic mutation to the UK of Greece as well as four people from Italy. Participants received brain exams and assessments.
While half of these participants had physical symptoms of Parkinson's disease, the other seven had no symptoms. The team also analyzed reviews and tests of 65 people with Parkinson's disease who did not have genetic mutations linked to the disease.
People with Parkinson's disease show a deterioration of systems in the brain that involve a neurotransmitter called dopamine, which would be behind certain symptoms such as slow motion. However, there were also signs of deterioration involving another brain chemical, serotonin.
The research revealed that, compared to scans of 25 healthy participants, scans of participants with physical symptoms of Parkinson's disease showed deterioration for both dopamine and serotonin systems in the brain – whether or not individuals had the genetic mutation.
A loss of serotonin neurons was observed in many brain regions of people who were genetically predisposed to Parkinson's disease but who had no physical symptoms. Politis observed that these individuals had a reduction of up to 34% in serotonin neurons compared to healthy participants.
The changes were seen about 15 to 20 years before these individuals began to exhibit physical symptoms. In addition, these genetically predisposed participants showed no signs of deterioration in their dopamine system. "That alone is a major breakthrough in how you view Parkinson's disease," said Politis.
He said the findings are exciting and could open the way for tests, or even offer ways to test new drugs to find out if they worked. "It's a whole new window on the disease," said Politis.
Roger Barker, a professor of clinical neuroscience at the University of Cambridge, said the findings confirm the suspicion that early signs of Parkinson's may not be found in the dopamine system. But he said doubts remain, including whether early changes in the serotonin system have been found in other groups at risk for Parkinson's, and whether those changes have progressed over time – and could predict reliably when physical symptoms may appear.
He noted that used scans were expensive and were not widely available, raising questions about how discoveries could be applied to filter people.
Beckie Port, manager of research communication at Parkinson's UK, said more research is needed, but suggested that the findings may raise new possibilities. "Currently, we can not give someone a brain exam to treat it earlier, slow or interrupt the condition, and perhaps prevent it from being diagnosed with Parkinson's. But with that finding, a future where this is possible seems a bit closer ".