Involuntary rhythmic movements of one of many body parts, known as tremors, are motor symptoms that manifest in over three quarters of patients with Parkinson’s disease. Tremors usually occur at rest and momentarily disappear with voluntary movement, returning when the body part is maintained in one position (fixed postural holding). They can occur at various frequencies. They typically occur in the fingers (often in a “pill rolling” motion involving the thumb and fingers) and the hands followed by the jaw and the feet, generally beginning on one side and often affecting the other as well as the disease progresses. Tremors can cause people affected with Parkinson’s disease to spill things, and can be irritating, as they are usually visible and can attract unwanted attention.
Research shows that tremor-dominant patients generally have a more benign disease than patients without tremors, as the progression of their disease tends to be slower. They also tend to have better cognitive performance and are less likely to develop dementia than non-tremor patients with Parkinson’s disease.
Tremors are thought to be linked to the altered action of two related brain circuits: that of the basal ganglia, primarily affected by dopamine depletion, which triggers the tremors episodes, and that of the cerebello-thalamo-cortical circuit, which produces the tremors. Brain imaging demonstrates increased connectivity between these two areas of the brain in patients with Parkinson’s, which supports the hypothesis that the basal ganglia initiates tremor responses, then interacts with the cerebello-thalamo-cortical circuit to fire neurons causing the limbs to shake.
Tremors often don’t respond as well to dopaminergic medication as other motor symptoms of Parkinson’s disease such as stiffness and mobility. That being said, if tremors remain severe or disabling after treatment with carbidopa/levodopa (which allow the conversion of levodopa to dopamine in the brain), other medications such as anticholinergic drugs, amantadine, propranolol or clozapine may be prescribed. Deep brain stimulation surgery is the most effective treatment for Parkinson’s-related tremors when medications fail, with a success rate of 90% of cases in which tremors resolve.
Exercise, on top of its well-documented health benefits, can help alleviate symptoms of Parkinson’s disease, improve cognition and contribute to slowing the progression of the disease. Given the voluntary movement involved during exercise, tremors disappear for the duration of the workout, which may be appealing to some people.
References
American Parkinson Disease Association (APDA). (2019, July 03). Tremor in Parkinson's. Retrieved December 14, 2020, from https://www.apdaparkinson.org/what-is-parkinsons/symptoms/tremor/
Helmich, R., Hallett, M., Deuschl, G., Toni, I., & Bloem, B. (2012, November). Cerebral causes and consequences of parkinsonian resting tremor: A tale of two circuits? Retrieved December 10, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3501966/
Mortkowitz, S. (2019, February 26). How Cycling Helps to Slow Down Parkinson's Disease. Retrieved December 14, 2020, from https://www.welovecycling.com/wide/2019/02/26/how-cycling-helps-to-slow-down-parkinsons-disease/
The Michael J. Fox Foundation. (n.d.). Exercise. Retrieved December 14, 2020, from https://www.michaeljfox.org/news/exercise?smcid=ag-a1b1R0000086fKy
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