Researchers have used imaging tools to show that Parkinson's disease may actually be two different diseases, one that starts in the brain while the other begins in the intestines. This can explain why patients can report very different symptoms and may improve therapeutic options for people that suffer from Parkinson's. The findings have been reported in the journal Brain.
"With the help of advanced scanning techniques, we've shown that Parkinson's disease can be divided into two variants, which start in different places in the body. For some patients, the disease starts in the intestines and spreads from there to the brain through neural connections. For others, the disease starts in the brain and spreads to the intestines and other organs such as the heart," said study author Per Borghammer of Aarhus University Hospital, Denmark.
In Parkinson's disease patients, the brain degenerates as a dangerous protein called alpha-synuclein accumulates. The nerve damage disrupts movement in patients.
PET and MRI imaging tools were used to assess Parkinson's disease patients as well as people who were thought to be at high risk for developing it. The work showed that there was damage in the dopamine systems in the brains of some patients prior to intestine or heart damage. In other patients, there was damage in the intestine's and heart's nerve networks before any damage appeared in the dopamine system of the brain. The findings, said Borghammer, challenge our understanding of the disease.
"Until now, many people have viewed the disease as relatively homogeneous and defined it based on the classical movement disorders. But at the same time, we've been puzzled about why there was such a big difference between patient symptoms. With this new knowledge, the different symptoms make more sense and this is also the perspective in which future research should be viewed," he said.
The scientists have referred to the two types as body-first or brain-first Parkinson's disease. They suggested that the microbiota may be of particular interest when it comes to body-first.
"It has long since been demonstrated that Parkinson's patients have a different microbiome in the intestines than healthy people, without us truly understanding the significance of this. Now that we're able to identify the two types of Parkinson's disease, we can examine the risk factors and possible genetic factors that may be different for the two types. The next step is to examine whether, for example, body-first Parkinson's disease can be treated by treating the intestines with feces transplantation or in other ways that affect the microbiome," explained Borghammer.
"The discovery of brain-first Parkinson's is a bigger challenge. This variant of the disease is probably relatively symptom-free until the movement disorder symptoms appear and the patient is diagnosed with Parkinson's. By then the patient has already lost more than half of the dopamine system, and it will therefore be more difficult to find patients early enough to be able to slow the disease," Borghammer noted.