Several specific regions in the brain cause tremor in Parkinson’s disease. Researchers at Radboudumc have discovered that there are also brain regions associated with a reduction of this symptom. This offers new opportunities for patients for whom existing treatments fall short.
Parkinson’s disease is characterized by the loss of cells that produce dopamine. This leads to symptoms such as slowness, stiffness, and tremor. Medication mainly replenishes dopamine and often works well for most movement problems, but less effectively for tremor. ‘It is precisely these tremors that many patients experience as the most troublesome symptom’, says physician-researcher Kevin van den Berg.
Remarkably, in people with Parkinson’s the severity of tremor often fluctuates. Stress and tension can make it worse, but strikingly there are also circumstances that reduce it. Small adjustments can sometimes make a big difference. What can help, for example, is moving the trembling hand itself or consciously focusing on relaxing it. Such tricks raise the question for researchers what happens in the brain when tremor decreases.
Tremor-suppressing network
Researchers therefore examined which brain areas are active when tremors diminish. ‘So far, the focus has mainly been on the regions that cause tremor’, explains neurologist Rick Helmich. ‘For a long time, we have ignored which brain areas actually slow the symptom down.’ This led researchers to discover the so-called anti-tremor network. The areas in this network play a role in two important functions: attention and body awareness.
New routes for treatment
The discovery of this network opens up new possibilities for treating tremor in Parkinson’s disease. ‘Currently, doctors target the brain areas that cause it, for example with medication or deep brain stimulation. But perhaps the key lies in strengthening this anti-tremor network’, says Van den Berg. ‘This could be done, for example, with external brain stimulation or new medications. It may also be possible to train these areas involved in attention and perception, for instance through mindfulness.’
First step
The researchers followed 119 people with Parkinson’s and simultaneously measured their brain activity and tremors. They used an MRI scanner: a device that creates images of tissues and organs, such as the brain. In addition, participants wore a motion sensor on their hand. By combining these data, the researchers mapped which networks are active when tremor increases or decreases.
Yet, the results should be interpreted with caution. The study mainly shows a correlation. To be certain whether this network can reduce tremor, researchers need to test whether symptoms decrease after actively intervening, for example with electrical stimulation. ‘Only then can you speak of a cause-and-effect relationship’, according to Helmich. One thing is clear, however: this discovery shifts the perspective. In Parkinson’s disease, there are not only brain networks that cause tremor, but also brain networks that suppress it. This provides new opportunities for treatments against tremor.
About the publication
This research was published in Brain: Large-scale antagonistic cerebral networks drive amplitude variability in Parkinson’s disease tremor. Kevin R.E. van den Berg, Martin E. Johansson, Filip Grill, Michiel F. Dirkx, Bastiaan R. Bloem, Rick C. Helmich. DOI: 10.1093/brain/awag182
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