Parkinson's disease is not one, but two diseases
Which explains why patients with Parkinson's describe widely differing symptoms, and points towards personalised medicine as the way forward for people with Parkinson's disease.
This is the conclusion of a study which has just been published in the leading neurology journal Brain.
The researchers behind the study are Professor Per Borghammer and Medical Doctor Jacob Horsager from the Department of Clinical Medicine at Aarhus University and Aarhus University Hospital, Denmark.
"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," explains Per Borghammer.
He also points out that the discovery could be very significant for the treatment of Parkinson's disease in the future, as this ought to be based on the individual patient's disease pattern.
Parkinson's disease is characterised by slow deterioration of the brain due to accumulated alpha-synuclein, a protein that damages nerve cells.
This leads to the slow, stiff movements which many people associate with the disease.
In the study, the researchers have used advanced PET and MRI imaging techniques to examine people with Parkinson's disease.
People who have not yet been diagnosed but have a high risk of developing the disease are also included in the study.
People diagnosed with REM sleep behaviour syndrome have an increased risk of developing Parkinson's disease.
The study showed that some patients had damage to the brain's dopamine system before damage in the intestines and heart occurred.
In other patients, scans revealed damage to the nervous systems of the intestines and heart before the damage in the brain's dopamine system was visible.
This knowledge is important and it challenges the understanding of Parkinson's disease that has been prevalent until now, says Per Borghammer.
"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 says. ■