Understanding the Root Cause of PSP and CBD: How Research in Tau Protein is Bringing Hope

Sep 08, 2025

One of the biggest challenges for people with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) is getting the correct diagnosis. These conditions are part of a group of diseases known as atypical Parkinsonism syndromes. This means that they share some symptoms with Parkinson’s disease, such as movement difficulties, stiffness and slow movements. But these diseases are quite different than Parkinson’s.

Since the early symptoms can look similar, many people living with PSP and CBD are first told they have Parkinson’s disease. But over time distinct features emerge. For example, PSP often causes difficulty in moving the eyes, and CBD causes one-sided movement difficulties or limb stiffness.

The root cause of these diseases and Parkinson’s is what makes them present differently. Parkinson’s occurs when a protein called alpha-synuclein builds up in the brain. Multiple system atrophy (MSA) is another disease caused by alpha-synuclein buildup. On the other hand, PSP and CBD are caused by problems with a protein in the brain called tau.

What is Tau Protein?

Protein is a nutrient that helps the body grow and work properly. Our bodies make proteins using instructions from our DNA. Just like a car needs different parts to run, the body needs different proteins to do important jobs. The tau protein is essential for keeping our brain cells functioning properly.

The tau protein (or just tau) helps support microtubules, which are like tiny highways inside brain cells. These highways carry nutrients and important information that tell the brain what to do. When tau acts normally, brain cells can communicate and function correctly. When tau isn’t working properly, it starts clumping together into tangles. These tangles disrupt normal brain cell activity. As a result, the brain cells shut down.

The tangled clumps of tau are key signs of several neurodegenerative diseases. In addition to PSP and CBD, Alzheimer’s disease is caused by a tau malfunction. However, Alzheimer’s is called a secondary tauopathy because the tau tangles contribute to the disease but aren’t the primary cause. PSP and CBD are primary tauopathies because tau dysfunction is the primary driver of the disease.

The Role of Tau Protein in PSP and CBD

The clumps of tau protein look different in each tau-related disease. This is what creates distinct symptoms. In PSP, the tau protein buildup occurs in the areas of the brain that manage movement, balance and thinking. Brain cells in these areas become damaged, causing the key symptoms of PSP:

Difficulty with balance and walking.
Problems moving the eyes, particularly looking up and down.
Stiffness and slowed movements.
Trouble swallowing and speaking.
Cognitive changes, such as difficulty with decision-making and impulsivity.

The tau clumps found in brains with CBD cause:

Asymmetric symptoms, or symptoms that start on just one side of the body.
Stiffness, shakiness or jerky movements.
Slowness and clumsiness.
Walking and balance difficulties.

Why Research on Tau Protein Is Important for PSP and CBD

Scientists are studying tau protein to better support people with PSP, CBD and other tauopathies. Understanding the clumps of tau could help researchers develop better diagnostics or even treatments.

Finding a reliable way to diagnose PSP and CBD is a top priority in brain health research.

One promising area of research is tau PET imaging. A PET scan shows detailed images of the body's organs and tissues. They’re currently used to detect and monitor different diseases, especially cancer. During these scans, doctors inject a special drug called a tracer into the person. The tracer looks for the disease so that it’s visible on the image.

In tau PET scans, the tracer attaches to tau tangles in the brain. This allows doctors to see the extent of tau buildup. Then, they can look for certain patterns in the buildup and find ways to diagnose different diseases. If doctors can learn about the different patterns of tau buildup and how to target the types of tau they can improve the use of tau PET scans. This improvement could enable doctors to diagnose PSP or CBD and differentiate them from other diseases.

Another area of tau research includes checking a person’s biomarkers (biological signals).  Biomarkers help doctors diagnose diseases and track their progression. A cholesterol test is an example of a biomarker. In PSP and CBD, researchers are exploring several biomarkers that can detect abnormal tau protein in the brain. These include cerebrospinal fluid (CSF), blood, and skin for abnormal tau levels.

By gaining a better understanding of abnormal tau protein and tau buildups, scientists can also work on developing therapies for people with PSP and CBD. Currently, there are studies for treatments that prevent tau from clumping altogether and ones that reverse tau buildup.

These studies are still in development, but they offer hope. Doctors could diagnose PSP and CBD earlier in their progression, and treatments could be more effective, especially if the disease is caught earlier. This is because the tau protein is easier to target when there is a smaller amount. Scientists hope that one day, these tests could even diagnose people before symptoms show up.

Looking Ahead: Research Offers Hope to People Affected by PSP and CBD

PSP, CBD and other tauopathies remain challenging to diagnose and treat. However, research is moving in the right direction. One of the key events advancing the field is the Tau Global Conference. This event brings together top scientists, clinicians and advocates to discuss the latest tau research. CurePSP plays a key role in this conference.

For patients and families affected by PSP, CBD and other tauopathies, this conference is another avenue for hope. Conference discussions could lead to the discovery of diagnostics, treatments and ultimately a cure.

As researchers continue to study tau protein, we know their hard work will bring us one step closer to a world where there’s a cure for PSP, CBD and other tauopathies. For now, it's crucial to raise awareness and support research.

Resources

CurePSP. (2023). Understanding PSP and Related Tauopathies. Retrieved from https://www.psp.org
Höglinger, G. U., et al. (2017). Clinical diagnosis of progressive supranuclear palsy: The Movement Disorder Society Criteria. Movement Disorders, 32(6), 853-864. DOI: https://doi.org/10.1002/mds.26987
Alzheimer’s Association. (2023). Tau and its Role in Neurodegeneration. Retrieved from https://www.alz.org/research/science/biomarkers
National Institute of Neurological Disorders and Stroke (NINDS). (2022). Progressive Supranuclear Palsy Fact Sheet. Retrieved from https://www.ninds.nih.gov
Litvan, I., et al. (2021). Tau biomarkers in neurodegenerative diseases: Advances in PSP, CBD, and Alzheimer’s research. Journal of Neurology, 268(5), 1800-1812. DOI: https://doi.org/10.1007/s00415-020-09722-3