Progressive supranuclear palsy is a disease that affects movement, thinking, speech and vision. It is called supranuclear palsy because "supranuclear" is the area of the brain that is affected and "palsy" means weakness or paralysis of a body part.

Common symptoms of PSP include: 

• Issues with balance and walking
• Frequent falls
• Changes to vision
• Difficulty with speech
• Early forgetfulness
• Personality changes
• Loss of interest in activities
• Impulsivity
• Increased irritability 

While these are some common symptoms that people first experience with the diagnosis, each person with PSP will experience the disease differently. Not everyone who has PSP will have all of these symptoms and no two people with PSP will have the same set or severity of symptoms.

At this time, there is no single test used to diagnose someone with PSP.

To diagnose PSP, a neurologist will gather a person’s medical history, including neurological symptoms, when they started, and how they impact the person’s everyday functioning. They will also perform a physical examination where they will evaluate how a person walks, speaks, and moves their eyes, feet and hands.

Neurologists will often refer to magnetic resonance imaging (MRI) to look for changes in the brain. On the MRI, there may be a noticeable atrophy found in the midbrain that resembles a hummingbird. The “hummingbird sign” on a MRI (sometimes called the “penguin sign”) can help to support a clinical diagnosis of PSP. A neurologist may decide to use other tests like blood tests, a neuropsychological evaluation, a DaTscan or positron emission tomography (PET) scan. These tests can help confirm a diagnosis of PSP or help rule out other causes of symptoms.

In some cases, a neurologist will gauge how someone responds to medications for Parkinson’s disease, which can also help a neurologist make a diagnosis of PSP.

Many people with PSP face a long and confusing diagnosis journey, including a number of tests, specialists, and diagnoses. It is our hope that better awareness of PSP, especially within the medical community, will lead to earlier and more accurate diagnosis.

PSP, like Parkinson's disease, is a movement disorder and features problems with movement and coordination. People with PSP tend to experience issues with balance, stiffness, coordination and slowness. Because of these symptoms, falls are a major concern for people with PSP. 

Slowed movements: Involuntary slowness of movement can be felt in the feet, legs, torso and neck, arms and hands.

Freezing of gait: The involuntary and temporary inability to move the legs and feet. This can happen at any time, but is most common when turning a corner or crossing through a doorway. 

Postural instability: Changes to the usual alignment of the body. This can be uncomfortable and also throw balance off.  

Rigidity: Muscles stiffen and create resistance to movement. This can make manual tasks more difficult, and can make it harder to regain balance, potentially causing falls. 

Dystonia: The contraction of muscles across legs, trunk and torso, arms, hands and feet. Some people with PSP might also experience these muscle contractions in the face.

Apraxia: The loss of the ability to carry out intentional movements. In PSP, this most commonly seen in speech and in the eyes. People with PSP might have a difficult time saying what they are thinking, which can feel frustrating to the person trying to speak. In apraxia of the eyes, people are not as able to control their eyelid movements and might experience a forceful closing of the eyes. 

As a reminder, no person with PSP will experience all of these symptoms, and each person will have their own severity of symptoms. There are many symptom management options and adaptive techniques for these symptoms, even as the disease progresses. 

Changes to vision can be an early symptom of PSP or a symptom that develops a few years after onset of symptoms. A neurologist or a neuropthomologist can help evaluate changes in eye function or vision. It's important to remember that not everyone with PSP will have all of these visual symptoms, and that symptoms vary by individual and in severity. 

Moving the eyes up and down: The most common and characteristic eye movement problem in PSP is an impaired ability to move the eyes up or down, known as eye movement apraxia. This is a symptom that is unique to PSP and distinguishes it from Parkinson's and general aging. Difficulty looking up and down can interfere with many daily activities, such as looking down at a plate while eating, descending a flight of stairs or stepping onto curbs. 

Jerky eye movements: PSP can cause the eyes to move in square, wavy jerks. These are rapid, involuntary, right-to-left movements that interfere with the ability to precisely aim the eyes at a target and make large movements of the eyes across the field of vision to become jerky rather than smooth. This can make it hard to read or maintain eye contact during conversation. 

Double vision: Many people with PSP report double vision, which can look like two images of one object or the images may overlap. This can be an early symptom of PSP and can be helped with prism glasses or prism stickers. 

Abnormal eyelid movement: There are different types of abnormal eyelid movements that people with PSP can experience.

• Involuntary closure of the eyelids: Known as blepharospasm, this can be either a forceful and involuntary eyelid closure that lasts a few seconds or minutes, or a difficulty initiating the opening of the eyelids. 
• Difficulty closing the eyelids or blinking: While most people blink about 15 to 25 blinks per minute, people with PSP tend to blink only about 3 to 4 times per minute. This can allow the eyes to become dry. Dry eyes can lead to blurred vision, production of extra tears, or a sensitivity to light called photophobia.

Treatment options: A neurologist or a neurophthalmologist can help provide treatment options for individual syptmoms. Examples of common treatments are artificial tears for dry eyes, prism glasses or prism stickers for double vision and Botox injections or eyelid crutches for forced eyelid closure. Occupational therapists can also provide recommendations for adaptations related to vision that can make daily life easier and the home environment safer.

The general area of the brain that is affected by PSP controls movements of the mouth, tongue and throat.

PSP can cause speech to have:

• An irregular, explosive, or rubber band quality (called spastic speech)
• A slurred, drunken quality (called ataxic speech)

These changes to speech and voice can be coupled with difficulty getting out thoughts or finding words, making communication quite challenging for many people with PSP. It can be helpful to work with a speech-language pathologist, especially one who is specialized in Parkinson’s disease and related disorders, to learn exercises and strategies to help people with PSP continue to communicate as much as possible.

PSP affects swallowing by causing weakness and incoordination of throat muscles. This can make it more difficult to swallow, which increases the risk of food or liquids going into the lungs, called aspiration. In some cases, aspiration can lead to pneumonia. Swallowing issues also make it more difficult for people to eat and drink, and can cause involuntary dehydration or weight loss. 

Changes to swallowing function can occur early in PSP. Signs of swallowing dysfunction can include:

• Coughing on thin liquids or more particulate foods, such as salads or dry cereal
  
• Often having the sensation of food being caught in the throat
• Having watery-sounding voice
• Choking often
• Recurrent lung infections
• Frequent runny nose 
• Sometimes people with PSP can eat more impulsively, including large bites or very quickly, which can also increase risk with swallowing

Your doctor may recommend regular examinations of your swallowing function to make sure food and liquid are going down the right way. Additionally, speech-language pathologists can help assess swallowing function as well as provide recommendations for diet and lifestyle modifications and exercises for the throat in order to make swallowing easier and safer.

There are different ways that PSP can affect cognition, and in different levels of severity. 

For many people, the initial concern is about developing dementia. To break it down, dementia is a term that refers to the loss of cognitive functioning to the extend that it impacts a person's daily life. There are different types and causes of dementia. In Alzheimer's disease, the most common cause of dementia, cognitive impairment is mostly in the area of memory. However, this is not the only form of dementia and does not automatically mean that people with PSP or related diseases will develop issues with memory. People with PSP tend to instead develop issues with processing and organizing thoughts, planning, multitasking, keeping attention and world-finding. 

Common cognitive issues that people PSP might experience: 

Aphasia: This is a cognitive deficit affecting communication, including finding words, expressing thoughts, and understanding language. Different neurological conditions can cause aphasia. Some people with PSP can experience aphasia. The severity can vary greatly, and for some, it can be an early symptom of PSP.

Impulsivity, poor judgment, and lack of insight: People experiencing these might not be aware of what their physical abilities are and complete movements that they are unable to accomplish .Impulsivity coupled with imbalance is the primary reason that people with PSP fall. For example, someone may jump up from a chair quickly, thinking they do not need to wait for assistance or use a walker, and fall. 

Some people with PSP will experience impulsivity as something like compulsive shopping. Many families struggle with the decision to have the person with PSP is adamant they can still drive or do other things safely when it is apparent to others that they are unsafe. 

Apathy: This can cause people to have less motivation to partake in activities. Cognitive changes in PSP can lead to social withdrawal or irritability, especially when they make communicating thoughts and participating in conversations more difficult.

Communication: Even in later stages of PSP, a person can often still respond to a question with accuracy and detail, but because of slowed processing speed, it may take several seconds or minutes and great effort to get out a thought. People with PSP and families can ask people to be patient when communicating. It can also be helpful to work with a speech-language pathologist on strategies to compensate for and adapt to cognitive changes and make communication easier.

PSP is not considered a genetic disease, but certain genetic variants have been found in those who have PSP. 

Scientists have found different variants in the tau protein gene on chromosome 17 that are more common in people with PSP compared to the general population. 

One of the variants is called the H1 haplotype. About 95% of people with PSP have this variant on both of their copies of chromosome 17, while this is true for only about 60% of people without PSP. Because of this, scientists believe that the H1 haplotype is likely needed, but far from sufficient, to cause the disease. This suggests that the H1 haplotype is almost necessary, but not sufficient on its own, to cause PSP. Scientists don’t yet know exactly how this gene variant impacts brain cells. It might cause the brain to produce more tau protein than normal or change how the protein works.

A handful of other gene variants that are not on chromosome 17 have been found to be more common in people with PSP than in people without PSP. These genes help control a variety of critical processes inside of brain cells. More research is needed to identify how these insights can translate into possible PSP prevention and treatment.

Genetic differences and exposure to certain chemicals are being explored as possible causes, but there is not currently an answer to why tau misfolds or people get PSP. For someone who is personally impacted by PSP, we recognize that not knowing the cause can be extremely frustrating, confusing, and scary. Researchers and doctors are working hard to understand PSP and other related neurodegenerative diagnoses, and we hope their work will lead to more answers and treatment options soon.

Read about the CurePSP Genetics Program to find out how you can help researchers learn more about how genes affect PSP, CBD and MSA. 

The name of the disease includes the word “progressive” because, unfortunately, early symptoms get worse and new symptoms develop over time. 

View CurePSP's resource "Stages of Progressive Supranuclear Palsy" for a general outline of what to expect in the future. 

Stages of PSP

Building a support team is foundational to the quality of life for the person diagnosed and their loved ones. Your support team may consist of your family, friends, support group, religious community, healthcare team and anyone else who cares about you. 

Download: Supporting Someone Diagnosed

Find the right medical team.  

Professionals that can help with symptom management, care planning and education may include: 

• A general neurologist, or ideally a movement disorder specialist  
• Primary care provider (PCP) 
• Nurse (NP, RN, CRN) 
• Physical therapist (PT) 
• Occupational therapist (OT) 
• Speech-language pathologist (SLP) 
• Clinical social worker (SW) 
• Nutritionist/Dietician  
• Pharmacist 
• Psychiatrist, psychologist or neuropsychologist 
• Ophthalmologist

Consider other care options. There are many options to help people with PSP get the care they need. People find huge benefits to hiring help to provide in-home care, utilizing community-based services such as adult day centers and choosing between many types of long-term care facilities. These services can provide additional layers of support, including companionship or hands-on help for the person with PSP and assistance and respite for the family. 

Quality of Life Respite Grant

Professional In-Home Care: Where to Start and What to Ask

Understanding Professional Long-Term Care

Connect with others who understand the experience.  

CurePSP has over 15 virtual national and international support groups, a vast network of regional support groups and music therapy and chair yoga sessions. Learn more about these great opportunities for community connection. 

In addition, CurePSP has Peer Supporters who are volunteers that have a direct connection to PSP, CBD or MSA and offer one-on-one emotional and practical support to individuals in the disease journey. Peer supporters can connect with people through phone, email or in-person meet-ups. Click here to find a Peer Supporter near you or to volunteer as a Peer Supporter.

No matter how you find support, please remember that you do not have to navigate the PSP journey alone. Connect with CurePSP at info@curepsp.org to learn more about resources and support.  

For many people with a diagnosis of PSP, the journey to a diagnosis was long and confusing.  It is common to have initially received a diagnosis of Parkinson’s disease because of the similarities in early symptoms

Carbidopa/levodopa: This is the main medication given to people with Parkinson's, and supplies dopamine to a part of the brain called the substantia nigra, which uses the medication to signal movement in the body. While the movement issues in Parkinson’s are mostly explained by damage in the substantia nigra, that area is only one of many affected areas in PSP. So, while the treatment works well for people with Parkinson’s, its benefit in PSP is unpredictable, usually modest and wears off after only a few years if there is any benefit.

When taking carbidopa/levodopa for PSP, it is recommended to take a standard form of the drug, rather than the controlled- or extended-release version. People with PSP might need a high dose of the drug and should be closely monitored by the healthcare team to watch for signs of cognitive issues or dizziness. People with PSP should be started on a low dose and gradually increase it to test tolerance and effectiveness. If there is no change in symptoms in two weeks, the maximum dose has been reached or there are any negative reactions to the medication, the medication can be tapered off and discontinued.  

The most common side effects can include nausea and sleepiness and issues with low blood pressure. 

Other Parkinson’s medications and their possible effect on PSP symptoms:  

Amantadine: This might have some benefit with gait issues, even if carbidopa/levodopa did not. Its benefit does not usually last more than a few months but can be useful for a short period. For people with PSP the dosage should not exceed 200mg per day because of potential cognitive side effects.  

Entacapone (Stalevo): Taken in conjunction with carbidopa/levodopa, entacapone slows down the rate at which dopamine is broken down. This will only have an effect for people whose symptoms show a clear response to carbidopa/levodopa and have a distinct medication wear off between doses. 

Dopamine receptor agonists: These drugs have no benefit in PSP beyond what carbidopa/levodopa can do. They are more likely to cause hallucinations, confusion, dizziness and nausea. 

Cholinesterase inhibitors: This class of medications has some benefit for cognitive loss in people with Parkinson’s or Alzheimer’s disease. With the possible exception of rivastigmine (Exelon), they have no benefit for people with PSP.  

Anticholinergic medications: Pure anticholinergic medications such as amitriptyline, trihexyphenidyl and benztropine might worsen gait and should be avoided in PSP.  

Medications that are not commonly used to treat Parkinson's disease, but may help with the Parkinsonism symptoms of PSP are: 

Donepezil: A common medication used to help treat the cognitive issues in Alzheimer’s, like memory and confusion. This medication has been found to help with the cognitive function in PSP but does worsen motor symptoms. The medication should be avoided in people with PSP because of increased fall risk and other side effects.  

Coenzyme Q-10 (CoQ10): This is an antioxidant that might be showing promise to help with gait and balance. If taken in a non-liposomal formula, the dosage should be between 1,200 – 2,400 mg per day. If taken in a liposomal formulation, about 300mg should be used per day. CoQ10 is not a prescription drug and therefore is not covered by insurance. Always discuss this option with a neurologist before starting the medication. 

A physical therapist (PT) helps people with movement symptoms. This is done through exercises during appointments that help strengthen or correct movements that are important for balance and coordination and continuing them at home. People with PSP should begin to see a PT when they notice any changes in balance or are having more difficulty getting around. An occupational therapist (OT) helps people continue doing tasks and activities that prolong independence and help maintain joy and meaning in their lives.

Reasons to see a physical therapist: 

• To prevent falls
• Issues with balance and walking
• Frequent falls
• Changes to vision
• Difficulty with speech
• Early forgetfulness
• Personality changes
• Loss of interest in activities
• To improve walking, with or without walking aids
• To increase safety when actively sitting or standing.
• To teach care partners safer ways of helping with transfers and walking.  

An occupational therapist (OT) helps people continue doing tasks and activities that prolong independence and help maintain a sense of joy and meaning in their lives. 

Reasons to see an occupational therapist: 

• To modify activities and hobbies so the person can still enjoy them, even if they can no longer do them as they once could.  
• To teach care partners how to safely complete activities of daily living, transfers and other caregiving tasks.   
  
• To discuss individualized needs for adaptive equipment and assistive devices like grab bars, weighted utensils or bed rails.  
• To be evaluated for canes, walkers or wheelchairs. 
• To find adaptations for activities of daily living that aren't as easy to do as they once were. This includes activities like showering, bathing, eating or writing. 

A speech-language pathologist (SLP) works with people who are having issues with speech, swallowing and language. Their goals are to improve and prolong communication skills, assess and help adapt to swallowing changes. 

Reasons to See a Speech-Language Pathologist: 

• To provide techniques that encourage good communication, verbally and non-verbally. 
• To learn about local and virtual programs that can help with speech symptoms. 
• To assess memory and thinking issues and make recommendations for adaptations. 
• To evaluate swallowing symptom progression.
• To evaluate speech symptom progression.
• To teach adaptive techniques for eating and swallowing to keep the person safe. 
• To prevent aspiration of liquids and food into the lungs. 

A feeding tube can be a safe and helpful option for people with PSP who are experiencing difficulties with swallowing. A feeding tube can be considered when someone is no longer able to take in necessary amounts of nutrition and calories by eating or drinking. They can prevent unnecessary weight loss and decrease risk of breathing in food or drink, known as aspiration. 

Getting a feeding tube placed means different things to different people, and there is no one right answer to whether or not someone should get on placed. Take the time to consider whether or not a feeding tube is right for you, before you need it. A feeding tube may be placed in some cases of emergency hospitalization, and if this is not a desire of yours, then be sure to state that in any advance directives. 

How is a feeding tube placed? Feeding tube placement is a surgical procedure done by a gastroenterologist (GI). The patient can be awake but sedated and it is often an outpatient procedure.  

How is a feeding tube used? Formula or pureed food is fed through the feeding tube into the digestive system through either a syringe or a feeding bag. There are many store-bought formulas available that provide necessary amounts of nutrition and calories. There is also the choice to make food at home using a blender. Some people choose to feed with both formula and pureed food. Water can also be given through the feeding tube, both for hydration and to keep the feeding tube clear of debris and blockages. 

In some cases, and only if discussed with the healthcare team, medication can be given through the feeding tube.

When living with a serious and progressive disease, it’s normal to experience sadness, uncertainty and fear about what the future may hold. These are normal emotions to process after receiving a life altering diagnosis — it requires a lot of emotional and physical energy to continually adapt to physical and mental changes! Like all feelings, these emotions are often temporary. However, when these normal emotions regularly interrupt your daily life and prevent you from participating in activities that you previously enjoyed, this could be a sign of a mental health issue.

People with PSP tend to experience depression and anxiety, but the most common mental health and mood symptom for people with PSP is apathy. Impulsivity and personality changes can also occur with PSP. While these symptoms can be isolating and scary, there are some treatment options to consider.  

Possible medications for depression and anxiety for people with PSP: 

• Selective serotonin reuptake inhibitors (SSRIs) 
• Serotonin and norepinephrine reuptake inhibitors (SNRIs) 
• Gabapentin

Warning: Tricyclic antidepressants (TCAs) are often used to treat insomnia, headaches and pain in the general population. However, for people with PSP, TCAs can impact cognitive function and should be avoided. For headache, topiramate can be considered instead.

Always speak with your neurologist before starting a mood medication. 

Non-drug methods for improving mood:

• Mental health therapy
• Cognitive behavioral therapy (CBT)
• Exercise
• A balanced diet
• Socialization
• Good sleeping habits
• Music
• Meditation 

Urgent mental health support options: 

• National Suicide Prevention Lifeline: 1 (800) 273-8255
• Now: 988 Suicide & Crisis Lifeline, dial/text 988.  
• The Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline: 1-800-662-4357
• Crisis Text Line: Text HOME to 741741

The direct cause of PSP is not fully understood. However, we do know that it has to do with the clumps of a protein called “tau”. Tau is a normal protein found in brain cells and is currently thought to help maintain the microtubules, which are stiff rods that function as the brain cells’ internal transportation and skeletal system. In PSP, the tau seems to become abnormally folded, which causes it to stick together and become stuck inside the cell. In brains with PSP, the areas of the brain that have cells with tau inside of them show neuron impairment and neuronal death. The clumps’ technical name is neurofibrillary tangles. Alzheimer’s disease and frontotemporal dementia also involve misfolding of the tau protein.

There is important research being done to look for genetic and environmental contributors to the cause of PSP, as well as research on tests that can lead to more accurate diagnosis and improved care of PSP. Many people with PSP find that participation in research is a meaningful way to help doctors and scientists understand, diagnose and treat PSP and related diseases. Additionally, participants in clinical trials may benefit from a new treatment that is not generally available and may receive detailed care and attention that is not part of routine medical care.

CurePSP Genetics Program: In collaboration with Massachusetts General Hospital, the National Institutes of Health and Indiana University, CurePSP is hosting a program with the aim of collecting genetic data from those with a PSP, CBD or MSA diagnosis. Get involved at psp.org/genetic-program. 

Clinical trials: In the United States, clinical trials are listed on a website maintained by the National Institutes of Health, www.clinicaltrials.gov. You can enter “progressive supranuclear palsy” into the search box. You can also ask your neurologist if they are aware of studies in PSP or consult curepsp.org for that information.

Brain Donation: Donating your brain to science can be a powerful contribution to the understanding of PSP and other neurodegenerative conditions. Each donated brain is also evaluated by a trained neuropathologist to confirm that the diagnosis of PSP was correct. Setting up brain donation needs to occur early, ideally months or even years prior to someone passing away. Visit www.psp. org/ineedsupport/braindonation to learn about CurePSP’s Brain Donation Assistance Program.

Building Partnerships: CurePSP is working hard to build partnerships with pharmaceutical and biotechnology companies to develop interest and funding for the study of PSP and related diseases. 

Funding Research: Additionally, CurePSP funds research through various grant programs and supports collaborative research projects through its growing CurePSP Centers of Care network of medical centers across the United States and Canada.

Subtypes of PSP happen because of small variations in the ways in which a person’s brain is affected by the accumulation and misfolding of the tau protein. When giving a diagnosis of PSP, a neurologist might specify the subtype they think the person has, or they might simply diagnose them with PSP.  

The two most common types of PSP are PSP-Richardson's Syndrome (PSP-RS) and PSP-Parkinsonsim (PSP-P). However, there are cases where people are diagnosed with other subtypes. 

Although it’s known that PSP-RS is the most common, it’s difficult to estimate how many people with PSP have which subtype. It’s hard to know because: 

• Statistics on PSP often exclude people who are unable to visit research insinuations due to barriers like cost and location.
• Many studies and trials focus exclusively on PSP-RS, overlooking other subtypes.
• Misdiagnosis of something other than PSP prevents many eligible patients from participating in clinical trials. 
• Most cases of PSP tend to resemble PSP-RS as the disease progresses, making it hard to identify subtypes if they are not noted early. 
• Clear clinical criteria for diagnosing PSP subtypes is not currently available. 

The most common initial symptom of PSP-RS is unexplained falls, but as the disease progresses, people might start to experience symptoms of other subtypes. Other common symptoms are issues with thinking and planning, controlling actions and speech, moving eyes up and down (supranuclear gaze palsy) and controlling the eyelids, swallowing, difficulty moving at a normal pace, ability to control the bladder and sleeping issues.  

PSP-Parkinsonism is the second most common subtype of PSP. Compared to PSP-RS, it has more asymmetry (one-sidedness), tremor and slowness. Compared to other types of PSP, PSP-P responds better to Parkinsonism medications, like levodopa. People with PSP-P tend to have fewer issues with thinking, behavior, balance and eye movement. It typically progresses the slowest of all the subtypes, averaging about nine years of survival after the first symptoms.  

PSP-P is often originally diagnosed as Parkinson’s disease because of the symptom similarities and the tendency for better and early responsiveness to Parkinson’s medications. It’s usually only when symptoms progress faster than expected that the medical team begins to rethink the Parkinson’s diagnosis. 

The main symptom of PSP-PGF is no longer being able to maintain an ongoing gait, or difficulty continuing walking after a step or two. This is especially true after pausing, turning or entering a doorway threshold. As the disease progresses, people with PSP-PGF usually can’t initiate walking at all. 

People with PSP-PGF may struggle with small handwriting and rapid speech. People that have issues with progressive gait freezing without other neurological symptoms are likely to eventually develop PSP.  

PSP-SL is a composite category, meaning that it is made up of other, smaller classifications that cover speech and language. Both subtypes in this category can have aphasia as a symptom. Aphasia is when someone has trouble mentally finding words, expressing thoughts or understanding language.   

People with PSP-SL experience a specific kind of aphasia, known as Primary Progressive Aphasia (PPA). This means that aphasia is caused by a progressive issue in the brain, rather than something like a stroke or a head injury. The two types of Progressive Aphasia in the PSP-SL category are:  

PSP-Nonfluent/Agrammatic variant of Primary Progressive Aphasia (PSP-nfaPPA): speech is halting with poor grammar and there is difficulty with syntax (sentence structure) and pronunciation. Comprehension and ability to name items and people are not affected.  

PSP-Semantic-Variant Primary Progressive Aphasia (PSP-svPPA): there is difficulty naming items and people but no issue with using proper grammar or syntax.  

PSP-CBS is highly asymmetric, meaning symptoms are usually only on one side of the body, or at least more prominent on one side. Symptoms tend to be rigidity, slowed movement and loss of skilled movement (called apraxia). It also features asymmetric fixed postures (called dystonia), weakness, abnormal reflexes (pyramidal findings) and small, rapid and irregular movements (known as myoclonus).  

People with PSP-CBS may also have a loss of visual perception, ability to identify familiar objects by touch or understanding where their body or limbs are in space. Aphasia, or difficulty understanding and pronouncing language, can sometimes happen.  

People with PSP-CBS have fewer issues with eyes, and less postural instability and cognitive loss than PSP-RS. CBS is a disease that is closely related to PSP, and it is sometimes given as a diagnosis by itself. 

PSP-F features some behavioral challenges, such as disinhibition, irritability, apathy and loss of empathy for others. It also is known for greater impairment in executive functions like maintaining attention, ability to follow instructions, changing tasks on command or stopping a behavior when attempting to.  

These specific cognitive and behavioral issues can be also found in PSP-RS but are usually milder than in PSP-F and only show up later in the disease. 

One of the main symptoms of PSP-RS is vision and eye symptoms. For people with PSP-OM, however, vision and eye trouble are one of the only features they experience. People with PSP-OM may have difficulty looking up or down, trouble tracking moving items with the eyes and other ocular problems. Issues with the eyes can sometimes cause falls in people with PSP-OM, because of problems in perception and sight.  

Another main symptom of PSP-RS is postural instability, which is trouble with balance, maintaining an upright posture and trouble walking. People with PSP-PI experience these parts of PSP-RS and might experience frequent falls due to these issues. Similarly to PSP-OM, this subtype features little else of the classic PSP-RS.  

PSP-PLS is a subtype of amyotrophic lateral sclerosis, known as ALS or Lou Gehrig disease. It can be difficult to tell ALS apart from PSP-PLS, but PSP-PLS is highly asymmetric and is similar to corticobasal syndrome (PSP-CBS). However, PSP-PLS rarely has the sensory loss, dystonia or the small and irregular movements that CBS is known for.  

The cerebellum is the area of the brain that’s located at the back of the head and helps control voluntary movement. PSP-C can cause balance and coordination problems and issues with vision and fine motor movements. Those with PSP-C have a lurching walk of PSP-RS (sometimes described as appearing as though the person is intoxicated), jerking movements of the eyes and slurred speech.  

It can be hard to tell PSP-C apart from PSP-RS while the person with the disease is still alive. When brain tissue is examined during autopsy, people with PSP-C are usually found to have shrunk cerebellums. 

For unclear reasons, this subtype is far more common in East Asia than elsewhere in the world. 

While there isn't currently a lot we know about PSP subtypes, there is much ongoing research around PSP subtypes. Some goals of this research are to: 

• Understand why PSP-RS and other cortical subtypes progress faster than subcortical subtypes, which would lead to more effective treatments. 
• Find better ways to diagnose and include people with PSP-RS subtypes in clinical trials. 

Regarding clinical trials only accepting those with PSP-RS, the reasons are because: 

• Less common PSP subtypes may react differently to drugs and treatments due to a small molecular differences from PSP-RS. 
• Because PSP-RS progresses more quickly than other subtypes, trials will have results in a shorter amount of time with fewer participants. 
• PSP-RS is usually confirmed by autopsy, 
• Most people who have early signs of PSP-RS are likely to be confirmed to have PSP at autopsy. However, with the other subtypes, there is a greater chance that people have other underlying conditions causing their symptoms, which could cloud the results of a drug study on PSP. 
• Almost all PSP trials measure outcomes using the PSP Rating Scale, which was designed to only measure PSP-RS. Because it was not designed to measure subtypes other than PSP-RS, other subtypes could cloud the data.