Researchers from the Faculty of Life Sciences at the University of Manchester, England, explained in the journal Brain Behavior and Immunity that severe stroke has been associated with Parkinson's. However, a significant number of people develop the tremors and other symptoms linked to the disease for no clear reason, "symptoms come out of the blue".
Several situations, diseases and conditions have been linked to a higher risk of Parkinson's disease, from exposure to vibrations and having severe flu. This is the first time scientists associated Parkinson's with silent strokes.
A silent stroke can occur without the sufferer even knowing about it - it may have no outward symptoms. A small stroke occurs when a blood vessel in the brain becomes blocked for a very brief period.
Although silent strokes may not be noticeable, they can have lasting effects. Dopaminergic neurons in the substantia nigra in the brain can die. The substantia nigra plays a key role in movement coordination.
Team leader, Dr. Emmanuel Pinteaux, said:
"At the moment we don't know why dopaminergic neurons start to die in the brain and therefore why people get Parkinson's disease. There have been suggestions that oxidative stress and aging are responsible. What we wanted to do in our study was to look at what happens in the brain away from the immediate area where a silent stroke has occurred and whether that could lead to damage that might result in Parkinson's disease."
Dr. Pinteaux and team induced a silent stroke like state (mild stroke) in the striatum area of the brain in laboratory mice. After the stroke, they detected inflammation and damage in the striatum - this was no surprise.
However, they noticed that another area of the brain - the substantia nigra - was also damaged. There had been a rapid loss of Substance P, a chemical which that region of the brain needs to function properly. There was also inflammation in the substantia nigra.
Neurodegeneration was also identified in the substantia nigra six days after the mild stroke - dopaminergic neurons had been destroyed.
Dr Pinteaux said: "It is well known that inflammation following a stroke can be very damaging to the brain. But what we didn't fully appreciate was the impact on areas of the brain away from the location of the stroke.
Our work identifying that a silent stroke can lead to Parkinson's disease shows it is more important than ever to ensure stroke patients have swift access to anti-inflammatory medication. These drugs could potentially either delay or stop the onset of Parkinson's disease.
What our findings also point to is the importance of maintaining a healthy lifestyle. There are already guidelines about exercise and healthy eating to help reduce the risk of having a stroke and our research suggests that a healthy lifestyle can be applied to Parkinson's disease as well."
Dr. Pinteaux would like to back up these findings on humans by examining patients who suffered a silent stroke, to assess dopaminergic neuron degeneration.
Until the new clinical investigation on humans is set up, the team are now trying to better understand what mechanisms are involved when inflammation occurs within the substantia nigra.
Written by Christian Nordqvist