Scientists say they have identified the first signs of Parkinson's disease in the brain – found 15 to 20 years before the symptoms appear.
Tests performed on a small number of patients considered to be at high risk showed dysfunction in the brain's serotonin system, which controls mood, sleep, and movement.
Researchers at King's College London who conducted the study say the finding could lead to new monitoring tools and treatments.
But, according to experts, it is necessary to conduct broader studies before and make the examinations more accessible.
Parkinson's is a progressive degenerative neurological condition that affects about 200,000 people in Brazil.
Among the main symptoms of the disease are tremors, involuntary movements and stiffness – depression, sleep problems and memory are also common.
Traditionally, it is believed that the disease is linked to a chemical called dopamine, missing in the brains of patients with the disease.
Although there is no cure, there are treatments to control the symptoms – and they focus on restoring dopamine levels.
But researchers at King's College suggest in an article in the journal Lancet Neurology that changes in the levels of serotonin in the brain happen first – and may act as an early warning sign.
The researchers analyzed the brains of 14 people from remote villages in southern Greece and Italy, all with rare mutations in the SNCA gene, making it almost certain to develop the disease.
Half of this group had already been diagnosed with Parkinson's, while the other half had no symptoms yet, making them ideal candidates to study how the disease develops.
Comparing the brains of this group with that of 65 other Parkinson patients and 25 healthy volunteers, the researchers were able to identify early brain changes in patients in their 20s and 30s.
The changes have been found in the serotonin system, a chemical that has many functions in the brain, including regulation of mood, appetite, cognition, well-being, and movement.
'Could open doors'
Lead author Marios Politis of the Institute of Psychiatry, Psychology and Neuroscience at King's College says the abnormalities were identified long before the movement disorders began and before the dopamine levels changed.
"Our results suggest that early detection of changes in the serotonin system could open doors for the development of new therapies to slow and ultimately prevent the progression of Parkinson's disease," he explains.
Derek Hill, a professor of imaging diagnostics at University College London (UCL) in the UK, says the research provided some valuable insights but also has some limitations.
"The results may not be escalated to larger studies," he says.
"Secondly, the imaging method used is highly specialized and limited to a very small number of research centers, so it is still not helpful in helping to diagnose patients or even to evaluate new treatments in large clinical trials."
"The research, however, encourages the approach of trying to treat Parkinson's as early as possible, which is probably the best opportunity to stop the growing numbers of people whose lives are being destroyed by this heinous disease."
Beckie Port, research manager at Parkinson's UK, UK, points out that further studies are needed:
"More research is needed to fully understand the importance of this discovery – but if it can reveal a tool that can measure and monitor how Parkinson's develop, it can change countless lives."
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