Unexplained Pain in Parkinson’s Disease

Targeted pain relief for Parkinson’s patients may be possible with targeted deep brain stimulation (DBS). Pain can occur for many reasons. It can be an early symptom of, or unrelated to, your Parkinson’s. Pain can be caused by some other condition or injury.¹ PD pain is underreported and undertreated because of variability in experiencing, tolerating, and tracking. Pain can have both physical and psychosocial effects impacting daily activities and family life. It can be treated in multiple ways including medication and deep brain stimulation.

Parkinson’s disease (PD) is a progressive, chronic movement disorder that is typically characterized by tremors, rigidity, and problems with gait and general smoothness of movement. People with Parkinson’s can experience motor and non-motor symptoms. Much has been written about psychological non-motor symptoms, but pain is another disruptive and disabling non-motor symptom of Parkinson’s.

Deep brain stimulation

Deep Brain Stimulation of the subthalamic nucleus has been used for years to control movement-related symptoms of Parkinson’s. A recent study from France suggests DBS can also be used to reduce the sensation of pain. Researchers have identified a novel brain network that senses pain in the subthalamic nucleus (STN). This area of the brain could be a potential target for pain relief in PD and other neurodegenerative disorders.^2,3 Findings on this new pathway, called a nociceptive network, were published in the journal eLife. The focus of the research was to evaluate whether the STN can convert a harmful stimulus like an injury to pain and whether this pathway is altered in people with Parkinson’s. The study used a rat model with PD, rather than people.

PD pain

PD pain can be related to motor symptoms or not. A doctor should help you identify the source of your pain as it may be caused by something other than Parkinson’s. The pain experience varies and for some may feel like a burning, stabbing, itching, or tingling sensation.² The researchers contend that symptoms not related to motor function may result from problems in the central nervous system.

Recent research

Research has been ongoing on the subthalamic nucleus area of the brain. This new research sought to evaluate any abnormal pain processing in the STN of rats using DBS.³ DBS treatments to the subthalamic area have been used to treat movement-related symptoms of Parkinson’s. The results from these recent studies demonstrate it also appears to reduce pain in animal models of PD.

Arnaud Pautrat, the lead author and his team from the Grenoble Institut des Neurosciences used electrophysiology (the study of electrical activity in the body) to measure the way electrical signals of nerve cells in the STN of rats react when given an electric shock in the back paw. They discovered that nerve cells were activated by this electronic stimulation. They reacted in three different ways; some had an increased response, some a decrease, and others experienced no change in the baseline firing rate of neurons.^3,4

Looking at rats with Parkinson’s, researchers discovered that nerve cells in the STN had higher firing rates and greater responses to pain than healthy rats. They believe this communication pathway is involved in creating the positive effects of DBS on pain. If DBS can block specific nerve activity it may be able to reduce the transmission of pain information.^3,5 This leads researchers to believe that DBS can stimulate certain areas of the brain to be beneficial for pain relief in people with Parkinson’s.

Target improved treatment options for Parkinson's

The team believes more research is required to better understand the impact of DBS on the subthalamic nucleus area of the brain caused by Parkinson’s, which will help to target the development of improved treatments for PD and other neurodegenerative conditions including Huntington’s disease and migraines.³