In a new study, researchers from the University of Manchester have for the first time identified why a patient who appears outwardly healthy may develop Parkinson's disease, a degenerative disorder of the central nervous system.
While conditions such as a severe stroke have been linked to the disease, for many sufferers the tremors and other symptoms of Parkinson's can appear to come out of the blue.
A silent stroke happens when a blood vessel in the brain is blocked for only a very short amount of time and often a patient won't know they have suffered from one.
However, it now appears that one of the lasting effects of a silent stroke can be the death of dopaminergic neurons in the substantia nigra in the brain, which is an important region for movement coordination.
"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 ageing are responsible," said Dr Emmanuel Pinteaux who led the research.
"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," Pinteaux said in a statement.
The team induced a mild stroke similar to a silent stroke in the striatum area of the brain in mice. They found there was inflammation and brain damage in the striatum following the stroke, which they had expected.
What the researchers didn't expect was the impact on another area of the brain, the substantia nigra. When they analysed the substantia nigra they recorded a rapid loss of Substance P (a key chemical involved in its functions) as well as inflammation.
The team then analysed changes in the brain six days after the mild stroke and found neurodegeneration in the substantia nigra. Dopaminergic neurons had been killed.
"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," Pinteaux said.
"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 on-set of Parkinson's disease," Pinteaux added.
The study was published in the journal Brain, Behavior, and Immunity.
