Progressive supranuclear palsy is a rare brain condition that gradually affects how people walk, move their eyes, speak, and think, causing serious challenges in daily life that worsen over time.

Understanding Progressive Supranuclear Palsy

Progressive supranuclear palsy, often shortened to PSP, is a rare and complex brain disease that damages specific areas deep within the brain. The name itself tells us something about what happens: “progressive” means the symptoms get worse over time, “supranuclear” refers to the location in the brain where damage occurs (above certain control centers), and “palsy” means weakness or difficulty controlling muscles. This condition is also known as Steele-Richardson-Olszewski syndrome, named after the doctors who first described it in detail in 1963.^[1][2]

The disease affects brain cells in areas that control body movement, balance, eye movement, thinking, and other vital functions. As these cells become damaged and die, people with PSP lose the ability to perform tasks that most of us take for granted. The condition belongs to a family of diseases called atypical parkinsonism, which means it shares some features with Parkinson’s disease but has its own distinct characteristics and progression.^[2][4]

What makes PSP particularly challenging is that it often gets mistaken for Parkinson’s disease, especially in the early stages. More than half of people with PSP are initially misdiagnosed with Parkinson’s disease. Healthcare providers usually begin to reconsider the diagnosis when symptoms progress faster than expected or when typical Parkinson’s medications don’t work as they should. Even for those who aren’t initially misdiagnosed, getting an accurate diagnosis can be a lengthy process because many healthcare providers are unfamiliar with this rare disease.^[5][16]

How Common Is Progressive Supranuclear Palsy?

PSP is considered a rare condition. Around 5 to 10 people out of every 100,000 have this disease, with approximately 30,000 cases in the United States. These numbers are likely underestimates because the condition is frequently misdiagnosed as Parkinson’s disease or frontotemporal dementia, which is a group of disorders affecting the front and sides of the brain.^[2][5]

To put this in perspective, about 1 million people in the United States have Parkinson’s disease, and about 7 million have Alzheimer’s disease. PSP is slightly more common than ALS (Lou Gehrig’s disease), but ALS is more widely known to the public, easier for doctors to diagnose, and often affects younger people, which may explain why it receives more attention.^[5]

The condition most commonly affects people over the age of 60, typically beginning in a person’s mid to late 60s. This is later than when Parkinson’s disease symptoms typically develop. It very rarely develops before the age of 40, though symptoms may start as early as in the 40s in some cases. PSP is slightly more common in men than women, but it has no known preference for any particular race, geographical location, or occupation.^[2][4][5]

What Causes Progressive Supranuclear Palsy?

Scientists don’t know the exact cause of progressive supranuclear palsy, but they do understand that a protein called tau plays a central role. Tau is normally an important protein that supports brain health and helps maintain the structure of brain cells. In healthy brains, tau is broken down properly before it reaches high levels. However, in people with PSP, tau isn’t broken down correctly and instead forms harmful clumps inside brain cells.^[2][3]

The amount of abnormal tau in the brain can vary among people with PSP, and the location of these clumps can differ as well. This means the condition can produce a wide range of symptoms, and not everyone experiences PSP in the same way. The accumulation of tau leads to the deterioration of cells in the brainstem (the lower part of the brain that connects to the spinal cord), cerebral cortex (the outer layer of the brain), cerebellum (which controls coordination), and basal ganglia (a cluster of cells deep within the brain). All these areas are crucial for movement, coordination, thinking, and other vital functions.^[1][3]

The condition has been linked to changes in certain genes, but these genetic changes aren’t inherited, which is an important point to understand. This means the risk to other family members, including the children or siblings of someone with PSP, is very low. PSP is not passed down through families in the way that some other genetic conditions are.^[3]

Risk Factors for Developing PSP

Currently, there are no well-established risk factors that clearly increase a person’s chance of developing PSP. The condition appears to occur randomly, without clear connections to lifestyle, environmental exposures, or specific behaviors. Unlike some other brain diseases, there are no known preventable risk factors such as diet, exercise habits, or exposure to toxins that have been definitively linked to PSP.^[3][5]

The main known factor is age, with most people developing symptoms in their 60s or later. Being male appears to slightly increase the risk, but this difference is small. The disease shows no preference for any particular race, occupation, or geographic region, suggesting that environmental and occupational factors don’t play a major role in who develops the condition.^[5]

Recognizing the Symptoms of PSP

The symptoms of progressive supranuclear palsy vary widely from person to person, and not everyone will experience all symptoms. They tend to begin gradually and typically become more severe over the years. Understanding these symptoms can help in recognizing the condition and seeking appropriate medical care.^[2]

The most common first signs of PSP include a loss of balance when walking or climbing stairs. This balance problem often leads to falling, and what’s particularly characteristic of PSP is that people tend to fall backward rather than forward, which is different from what happens with Parkinson’s disease. These unexplained falls can occur very early in the disease, sometimes within the first year or two of symptoms appearing. Another early symptom that many people notice is difficulty looking downward with their eyes, along with a wide-eyed, staring facial expression.^[1][2][4]

As the disease progresses, most people develop a range of eye problems. These can include slow eye movements, trouble looking up or down, difficulty controlling the eyelids (which may close involuntarily or be hard to open), decreased blinking, and a tendency to move the entire head rather than just the eyes to look in different directions. Some people experience blurred or double vision. These vision difficulties can make everyday tasks like reading, going down stairs, or making eye contact during conversations particularly challenging. The decreased blinking can also lead to sensitivity to bright light, and some people need to wear sunglasses even indoors to avoid irritation.^[1][4][7]

Many people with PSP also experience stiff muscles that affect their ability to move freely. This stiffness tends to affect the neck and trunk more than the limbs, causing people to walk, turn, and sit as a rigid “block.” The muscles in the mouth, tongue, and throat can also become weakened, leading to difficulty swallowing (dysphagia) and slurred, slow, or monotone speech. Swallowing problems can cause choking or gagging and may lead to a serious complication called aspiration pneumonia, which occurs when food or liquid goes down the windpipe into the lungs instead of the food pipe into the stomach.^[1][5][7]

PSP also affects thinking and behavior. People with the condition and their loved ones often notice changes in mood and personality. These may include depression, lack of motivation or interest in activities they used to enjoy (apathy), increased irritability, changes in judgment and problem-solving abilities, difficulty finding the right words, forgetfulness, and sudden outbursts of laughing, crying, or anger for no apparent reason. Some people develop dementia, which involves a decline in memory, thinking, and reasoning skills severe enough to interfere with daily life. Personality changes and impulsivity, which involves acting without thinking through the consequences, are also common.^[2][4][5]

Sleep problems are another symptom that many people with PSP experience. These can include insomnia (difficulty falling or staying asleep) and REM sleep behavior disorder, a condition where people act out their dreams during sleep, sometimes violently, which can be dangerous to themselves or their bed partners.^[2]

Different Types of PSP

Healthcare professionals have identified different types, or subtypes, of PSP based on which symptoms are most prominent. These subtypes all share similar underlying causes but can look quite different in how they affect people.^[2]

The most common subtype is called Richardson syndrome (PSP-RS). This form typically includes balance problems with frequent falls (often backward), difficulty controlling eye movements (especially looking down), a wide-eyed staring expression, abnormal speech, and problems with memory and thinking. People with Richardson syndrome usually experience stiffness more in their trunk and neck than in their arms and legs. This subtype accounts for the majority of PSP cases.^[2][7]

Another common subtype is the Parkinson’s disease-like variant (PSP-P), which resembles Parkinson’s disease more closely than Richardson syndrome does. In this form, tremor (involuntary shaking) is the main symptom instead of balance problems and behavioral changes. People with PSP-P may respond better to medications used for Parkinson’s disease, at least for some time, compared to those with other types of PSP. Together, Richardson syndrome and PSP-P make up about 75% of all PSP cases.^[2]

Other, less common subtypes include corticobasal syndrome and pure akinesia with gait freezing. Each of these has its own pattern of symptoms, though all ultimately involve the same underlying disease process with tau protein accumulation in the brain.^[2]

How PSP Differs from Parkinson’s Disease

PSP is sometimes called an “atypical parkinsonism” because it shares some symptoms with Parkinson’s disease, such as balance problems, stiffness, slowness, and clumsiness. However, PSP and Parkinson’s disease have their own unique sets of symptoms and progress differently because they have different underlying causes. Understanding these differences is important for getting the right diagnosis and treatment approach.^[4][5]

One key difference is the direction of falls. People with PSP tend to fall backward and often extend their neck, a pattern called “axial rigidity.” In contrast, people with Parkinson’s disease tend to bend forward rather than backward and usually fall forward when they do fall. This difference in posture and fall direction can be an important clue for doctors trying to distinguish between the two conditions.^[4][14]

Tremor is another distinguishing feature. While tremor, especially a resting tremor (shaking that occurs when muscles are relaxed), is a characteristic symptom of Parkinson’s disease, people with PSP typically do not experience tremor, or it’s much less prominent. On the other hand, the eye movement problems that are so characteristic of PSP, particularly difficulty looking downward, are not typically seen in Parkinson’s disease.^[4][5]

The response to medication is also quite different. People with Parkinson’s disease often get significant relief from medications like levodopa (often combined with carbidopa in a medication called Sinemet). While some people with PSP may see slight improvement with these medications, the response is usually limited and temporary, often lasting only about 2 to 3 years at most. When typical Parkinson’s medications don’t provide the expected benefit, doctors may begin to suspect PSP instead.^[5][8]

Perhaps the most important difference is the rate of progression. PSP typically progresses much more rapidly than Parkinson’s disease. Most people with PSP develop severe disability within three to five years of symptom onset, whereas Parkinson’s disease typically progresses more slowly over many years. This faster progression is often what prompts doctors to reconsider an initial diagnosis of Parkinson’s disease.^[4][5]

Can PSP Be Prevented?

Unfortunately, there are currently no known ways to prevent progressive supranuclear palsy. Because scientists don’t fully understand what causes the disease, and because there are no clear environmental or lifestyle risk factors that have been identified, there are no specific prevention strategies that can be recommended. The condition appears to occur randomly, without connection to factors that people can control or modify.^[2][3]

This is different from some other brain conditions, like stroke or certain types of dementia, where lifestyle factors such as controlling blood pressure, maintaining a healthy diet, exercising regularly, and avoiding smoking can reduce risk. For PSP, no such preventive measures have been established. The genetic changes associated with the disease are not inherited, so even people with a family member who has PSP don’t have a significantly increased risk themselves.^[3]

However, once someone has been diagnosed with PSP, there are important steps that can be taken to manage complications and maintain quality of life. Fall prevention strategies, such as removing tripping hazards from the home and using assistive devices like walkers, can help reduce injuries. Working with speech and language therapists can help manage swallowing difficulties and reduce the risk of aspiration pneumonia. These supportive measures, while not preventing the disease itself, can help people with PSP live more safely and comfortably.^[9]

What Happens in the Brain with PSP

Understanding what happens inside the brain in PSP helps explain why the symptoms occur. The disease causes damage to nerve cells in specific brain regions that control movement, thinking, and body functions. This damage results from the buildup of abnormal tau protein, which forms clumps inside brain cells and causes them to malfunction and eventually die.^[1][2]

The brainstem, which is the lower part of the brain connecting to the spinal cord, is particularly affected. This region controls many automatic functions and helps coordinate movement. When cells here are damaged, it affects balance, eye movements, and the muscles involved in speaking and swallowing. The basal ganglia, a cluster of structures deep in the brain that help control movement and coordination, also sustain significant damage. This explains the stiffness, slowness of movement, and difficulty with walking that people with PSP experience.^[1][7]

The cerebral cortex, which is the outer layer of the brain responsible for thinking, memory, and decision-making, is affected as well. Damage here leads to the cognitive and behavioral changes seen in PSP, including problems with memory, judgment, personality changes, and eventually dementia in some people. The cerebellum, which helps coordinate movement and maintain balance, also shows deterioration, contributing to the balance problems and falls that are so characteristic of the condition.^[1]

The part of the brain that controls eye movement is located in a specific area of the brainstem. In PSP, the damage occurs above these eye-moving centers (hence the term “supranuclear”), disrupting the signals that allow us to voluntarily move our eyes. This is why people with PSP have such distinctive eye movement problems, particularly difficulty looking up and down, even though the muscles and nerves that directly control the eyes are still working properly.^[2][7]

As more brain cells die over time, the symptoms become more severe and widespread. Brain imaging studies using MRI can sometimes show shrinkage (atrophy) in specific brain regions associated with PSP, particularly a characteristic pattern in the midbrain that doctors call the “hummingbird sign” because the shape resembles the silhouette of a hummingbird. This pattern can help distinguish PSP from other conditions.^[8]