Pain is a sensation that is difficult to understand in people with or without Parkinson’s Disease (PD). How pain is perceived is a long winding road that involves many areas of the nervous system.
The path the message of pain takes starts at receptors in the skin and travels up the spinal cord to the brain. Once the signal reaches the brain, it travels to many different areas involved in perception and attention including areas of the brain involved in emotion. Because of the connection to the parts of the brain involved in emotion, the pain experienced may be modified as a function of beliefs, emotions, and expectations of the specific person.
Understanding how we perceive pain helps us understand how having PD can cause individuals to have increased pain. The perception of pain can be affected and altered in several areas of the pain pathway.
First, the receptors that initially receive the signal of pain can be impaired, amplifying the signal. For example, soft touch can be perceived as painful. It can be compared to taking a wrong turn at the start of a road trip causing your GPS to recalculate a new different route.
Second, the highways the message of pain takes to get to the brain can affect the perception of pain, slowing down the message and decreasing the speed to which the body can react to the stimulus.
Finally, the higher order areas of the brain can be affected through a decrease in dopamine and through the accumulation of proteins in the brain. The decrease in the production of dopamine can affect the pathways directly by enhancing or diminishing the signal for pain and indirectly by influencing the expectation, experience, and interpretation of signals for pain. The accumulation of proteins can cause roadblocks in the messaging affecting how pain is perceived as well.
People with PD can also experience more pain due to the motor symptoms of the disease. Muscle and skeletal pain can develop from changes in posture, abnormal movement patterns or muscle contractions.
Pain in people with PD is something that is complex, difficult to understand, and can be a frustrating symptom to experience in addition to other symptoms. Understanding how Parkinson’s disease can change how pain is perceived or cause more pain can be the first step in working to decrease pain and improve quality of life.
Rukavina K, Leta V, Sportelli C, et al. Pain in Parkinson's disease: new concepts in pathogenesis and treatment. Curr Opin Neurol. 2019;32(4):579-588. doi:10.1097/WCO.0000000000000711
Karnik V, Farcy N, Zamorano C, Bruno V. Current Status of Pain Management in Parkinson's Disease. Can J Neurol Sci. 2020;47(3):336-343. doi:10.1017/cjn.2020.13