Researchers Identify Possible Cause of Chronic Pain in Parkinson’s Patients

Chronic pain affects about two-thirds of those with Parkinson’s, making it the major non-motor symptom of the disease. A study published in Movements Disorders has found that anandamide and glucocerebroside levels are altered in those with Parkinson’s and can lead to sensory nerve damage. This data coincides with previous studies, which discovered that a dysfunctional endocannabinoid system, damage to the sensory nerves, and poor inhibitory pain control all play a role in chronic pain.

About Parkinson’s Disease

Parkinson’s disease is a progressive disorder that affects the central nervous system (CNS). It is characterized by its effect on movement through five different stages. As the disease progresses, severity increases.

Stage one is characterized by subtle tremors on one side of the body. In stage two symptoms are more noticeable, with tremors and rigidity on both sides of the body. Stage three brings loss of balance and slowed movement. Stage four makes it impossible for one to live independently. Stage five is the most severe, as patients cannot stand or walk. Hallucinations and delusions are common symptoms of this stage.

Parkinson’s disease occurs due to the death of motor neurons, some of which produce dopamine. Dopamine is important in the transmittance of messages to the muscles from the brain, so the loss of dopamine results in the loss of motor functions. Abnormal brain activity occurs when these neurons are lost. Doctors do not know why these motor neurons die, but they do suspect a few factors that play a role, such as genetics, environmental factors like toxins, and Lewy bodies.

Chronic Pain in Parkinson’s

Past research has found that the dysregulation of fatty molecules, such as anandamide and glucocerebroside, could lead to the progression and development of the disease. This could be due to low levels of beta-glucocerebrosidase, an enzyme needed to break down glucocerebroside. But while prior research points to the dysregulation of fatty molecules, there is little supporting evidence.

To further investigate chronic pain in Parkinson’s, researchers in Israel and Germany began studying sensory issues and unbalances of various fatty molecules. Two groups of patients participated in the study, one was 128 Parkinson’s patients from Israel with 224 healthy people as a control, while the other was 50 German Parkinson’s patients and 50 healthy controls.

Through the use of questionnaires, intensity ratings, and quantitative sensory tests (QST), the scientists evaluated symptoms of pain and sensory loss in the patient groups. Researchers also measured the levels of fatty molecules in the blood. The two groups of patients displayed similar results. 74% of German Parkinson’s patients experienced chronic pain, compared to 66% of the Israeli Parkinson’s patients. Within the control group, 40% reported chronic pain. In terms of sensory impairment, Parkinson’s patients experienced a loss of thermal and vibration perception and an increased sensitivity to mechanical pain. Lastly, Parkinson’s patients had high levels of glucocerebrosides and low levels of anandamide.

All of these results show that with or without chronic pain, Parkinson’s patients show sensory dysfunction that is at least partly associated with altered levels of fatty molecules. Finding the cause is very helpful, as it can help medical professionals find treatments. In fact, they believe that cannabis-based products and certain Gaucher disease therapies could be helpful.

Read more about this research here.

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