When Blood Pressure Drops: What’s Really Going On in Parkinson’s Orthostatic Hypotension

Many people with Parkinson’s disease know the dizzy spell that comes with standing up too quickly. This drop in blood pressure, known as orthostatic hypotension (OH), is surprisingly common in Parkinson’s—affecting between 30 and 50 percent of people. For some, it causes light-headedness or fainting. For others, it quietly worsens outcomes without obvious symptoms. For years, doctors thought OH in Parkinson’s was mainly caused by damage to the peripheral nerves—the ones that control heart rate and blood pressure outside the brain. But a new study led by Dr Laura de Lima Xavier and colleagues at the University of North Carolina challenges that view. It shows that the brain itself, not just the body, plays a crucial role in this form of blood pressure failure. ⸻ The Brain Networks Behind Autonomic Control Our blood pressure, heart rate, and other “automatic” functions are controlled by a system called the autonomic nervous system. It operates partly through a group of brain regions known as the Central Autonomic Network (CAN). This network links areas deep in the brain to higher regions that process emotion, attention, and bodily awareness. One key player is the salience network, a system anchored in the anterior cingulate cortex (ACC) and the insula. This network acts as a sort of internal spotlight, deciding which sensations and signals—like hunger, pain, or standing up—deserve the brain’s attention. It also helps regulate the body’s physical response to these signals, including changes in blood pressure. Both the CAN and salience network are known to be affected in Parkinson’s. The regions that form them are often hit by Lewy body deposits—the abnormal protein clumps that damage neurons in PD. This raised an intriguing question: could disruptions in these brain networks explain why some people with Parkinson’s struggle to maintain blood pressure when they stand up? ⸻ Peering Into the Brain To explore this, the team studied 31 people with Parkinson’s using two main tools: autonomic reflex testing, which measures how the body responds to changes in posture, and functional MRI (fMRI), which maps how different parts of the brain communicate. Of the 31 participants, 11 had orthostatic hypotension. When the researchers compared their brain scans with those who didn’t have OH, clear differences emerged. Connectivity—the degree of coordinated activity—was weaker between key nodes of the salience network, including the anterior cingulate cortex, both sides of the anterior insula, the rostral prefrontal cortex, and the supramarginal gyrus. Importantly, these connectivity gaps were directly linked to the severity of blood pressure drops and symptoms of autonomic dysfunction. In other words, the weaker the brain’s communication in these areas, the worse the blood pressure control. No such changes were found in unrelated brain networks, suggesting the problem was specific to systems that handle autonomic control. ⸻ What It Means This study provides solid evidence that orthostatic hypotension in Parkinson’s is not only a peripheral issue but also a central one—a failure of brain networks that coordinate automatic body functions. It paints a more complete picture of how Parkinson’s disrupts the body’s control systems, extending beyond the loss of dopamine and movement problems we usually hear about. The salience and CAN networks, normally busy fine-tuning our internal balance, appear to lose their synchrony in Parkinson’s, making it harder for the brain to keep blood pressure steady when standing up. The discovery is more than academic. By pinpointing where these central breakdowns occur, researchers can now explore new treatment options. Neuromodulation—techniques that stimulate specific brain areas with electrical or magnetic pulses—could one day help restore communication within these networks and ease the symptoms of orthostatic hypotension.