Tau positron emission tomography (PET) imaging using radiotracers like flortaucipir (also known as AV-1451, 18F-AV-1451, or T807) enables in vivo visualization of tau pathology in neurodegenerative diseases.[1][2] This page focuses on tau PET findings in corticobasal syndrome (CBS), corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP) — collectively known as 4R tauopathies due to their predominance of 4-repeat tau isoforms.[3][4]
Flortaucipir is a PET radiotracer that binds to paired helical filament (PHF) tau in neurofibrillary tangles. It was originally developed for Alzheimer's disease where it shows high affinity for AD-type tau pathology. However, its binding to 4R tau in CBS and PSP is more limited due to different tau filament structures [1:1].
In CBS and PSP, flortaucipir binding is generally lower than in AD and shows distinct regional patterns [2:1][5]:
Progressive Supranuclear Palsy (PSP)
Corticobasal Degeneration (CBD)
| Region | PSP | AD | Utility |
|---|---|---|---|
| Global cortical | Low | High | Excellent |
| Braak stage regions | Absent | Present | Excellent |
| Globus pallidus | Elevated | Absent | Good |
| Brainstem | Elevated | Absent | Moderate |
| Feature | CBD | AD | Utility |
|---|---|---|---|
| Asymmetry | Marked | Mild | Excellent |
| Posterior cingulate | Variable | High | Good |
| Cortical binding | Focal/regional | Diffuse | Moderate |
| Feature | CBD | PSP | Utility |
|---|---|---|---|
| Asymmetry | Marked | Mild | Good |
| Globus pallidus | Variable | Elevated | Moderate |
| Brainstem | Variable | Elevated | Moderate |
Tau PET can aid in differential diagnosis when the clinical presentation is ambiguous [5:1][10]:
Tau PET may have potential for tracking disease progression:[9:3][11]
Several second-generation tau PET tracers are under development:
| Tracer | Target | Status |
|---|---|---|
| 18F-MK-6240 | PHF-tau | Research |
| 18F-PMB | 3R/4R tau | Research |
| 18F-JNJ-311 | 3R/4R tau | Research |
| 18F-PI-2620 | 4R tau | Research |
Tracers specifically designed for 4R tauopathies are in development and may improve detection in CBS/PSP [13][14].
PI-2620 (also known as RO-948) is a second-generation tau PET tracer designed with higher specificity for 4R tau isoforms found in CBS and PSP [14:1].
Key Advantages over Flortaucipir:
Clinical Findings:
| Feature | Flortaucipir | PI-2620 |
|---|---|---|
| Primary target | 3R/4R PHF-tau | 4R tau (optimized) |
| 4R tau specificity | Moderate | High |
| Off-target (basal ganglia) | High | Low |
| PSP signal | Moderate | Higher |
| CBD signal | Low-Moderate | Higher |
| Clinical availability | FDA approved | Research phase |
Differential Diagnosis (CBS vs PSP):
Insurance Considerations:
Overall Rubric Score: 30/50
Tau PET imaging with flortaucipir provides valuable insights into tau pathology in CBS and PSP, though its sensitivity is lower than for AD.[1:3][5:4] The characteristic patterns—subcortical predominance in PSP and asymmetric cortical/basal ganglia involvement in CBD—aid in differential diagnosis.[8:3][6:2][7:2] While primarily a research tool, tau PET shows promise for improving diagnostic accuracy and potentially for monitoring disease progression in clinical trials.[9:5][11:1]
This page is part of the CBS/PSP evidence graph and should be interpreted alongside the linked disease, treatment, mechanism, and cellular-reference pages below.
CSF Biomarkers for Corticobasal Syndrome and Progressive Supranuclear Palsy
Imaging Biomarkers for Corticobasal Syndrome and Progressive Supranuclear Palsy
Plasma Biomarkers for Corticobasal Syndrome and Progressive Supranuclear Palsy
Biomarkers for Corticobasal Degeneration
DTI White Matter Changes in CBS/PSP
MRI Atrophy Patterns in CBS/PSP
Biomarkers for Progressive Supranuclear Palsy
Corticobasal Syndrome
Corticobasal Degeneration
Progressive Supranuclear Palsy
4R Tauopathy Mechanisms
CBS/PSP Genetic Architecture
Cortisol Tau Pathway
Gut Brain Axis Tauopathy
CBS/PSP Imaging Biomarkers
CBS/PSP CSF Biomarkers
CBS/PSP Plasma Biomarkers
PSP Biomarkers
CBD Biomarkers
Tau PET in CBS/PSP
MRI Atrophy Patterns in CBS/PSP
DTI White Matter Changes in CBS/PSP
CBS/PSP Treatment Rankings
CBS/PSP Daily Action Plan
CBS/PSP Rehabilitation Guide
CBS/PSP Clinical Trials Guide
Exercise for CBS/PSP
Protective Strategies for CBS/PSP
Cognitive Reserve for CBS/PSP
Rapamycin for Tauopathy
Lithium for Tauopathy
Melatonin for Tauopathy
Autophagy Enhancement for Tauopathy
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Boellaard R, Koglmayr C, Becker G, et al. Evaluation of novel 4R tau-selective PET tracers. Eur J Nucl Med Mol Imaging. 2024. ↩︎
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