Imaging Biomarkers for Corticobasal Syndrome and Progressive Supranuclear Palsy

Overview

Neuroimaging plays a crucial role in the diagnosis, differential diagnosis, and understanding of underlying pathology in corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP). Both structural and functional imaging modalities provide valuable information for distinguishing these disorders from each other and from other neurodegenerative parkinsonian disorders. [@review2025]

Asian Population Considerations

Overview

Neuroimaging plays a crucial role in the diagnosis, differential diagnosis, and understanding of underlying pathology in corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP). Both structural and functional imaging modalities provide valuable information for distinguishing these disorders from each other and from other neurodegenerative parkinsonian disorders. [@review2025]

Asian Population Considerations

CBS and PSP imaging patterns have been studied in Japanese, Korean, and Chinese populations, revealing population-specific nuances:

• Brain volume differences: Asian populations show smaller average brain volumes, affecting volumetric cutoffs
• Atrophy patterns: Consistent with Western populations but with adjusted regional thresholds
• FDG-PET hypometabolism: Similar patterns observed across Asian cohorts
• Midbrain to pons ratio: May differ due to population-specific brain size variations
• DTI metrics: Comparable sensitivity and specificity in Asian populations
• Diagnostic cutoffs: Studies from J-ADNI, Korean, and Chinese cohorts provide validated cutoffs

Structural MRI Findings

Cortical Atrophy Patterns

CBS-Specific Atrophy

• Asymmetric cortical atrophy: Contralateral to more affected side
• Precentral gyrus involvement: Characteristic "knife-edge" atrophy
• Parietal lobe atrophy: Especially superior parietal lobule
• Frontal atrophy: Including orbitofrontal regions
• Temporal involvement: Often less prominent than frontal/parietal

PSP-Specific Atrophy

• Midbrain atrophy: "Hummingbird sign" on sagittal images
• Superior cerebellar peduncle atrophy: Characteristic finding
• Globus pallidus atrophy: T2 hypointensity
• Thalamic atrophy: Dorsomedial nucleus involvement
• Frontal lobe atrophy: Particularly superior frontal gyrus

Differential Patterns

| Region | CBS | PSP | [@multimodel2026]
|--------|-----|-----| [@realworld2026]
| Motor cortex | Asymmetric, severe | Symmetric, moderate | [@current2026]
| Parietal lobe | Prominent atrophy | Less affected | [@automated2026]
| Brainstem | Less affected | Midbrain prominent | [@molecular2026]
| Cerebellum | Variable | Superior peduncle |

Quantitative MRI Measures

• Cortical thickness: Reduced in CBS, helps quantify atrophy
• Subcortical volumes: Basal ganglia, thalamus measurements
• Diffusion tensor imaging: White matter tract integrity

Functional Imaging

FDG-PET Findings

CBS Hypometabolism Patterns

• Asymmetric hypometabolism: Contralateral to clinically affected side
• Posterior cortical regions: Parietal-occipital predominance
• Precentral gyrus: Motor cortex involvement
• Thalamic hypometabolism: Ipsilateral to cortical findings
• Striatal patterns: Putaminal > caudate

PSP Hypometabolism Patterns

• Brainstem: Midbrain prominent
• Frontal cortex: Particularly superior frontal
• Globus pallidus: Characteristic finding
• Thalamus: Dorsomedial nucleus
• Cerebellar: Less prominent than brainstem

Diagnostic Utility

• FDG-PET can distinguish CBS from PSP with ~80-90% accuracy
• Asymmetry helps differentiate CBS from PSP
• Combined with clinical data improves diagnostic confidence
• Specificity exceeding 90% in some studies

Tau PET Imaging

18F-Flortaucipir (FTP)

• Binds to tau neurofibrillary tangles
• Elevated in CBS-AD but not in CBS-PSP/CBS-CBD
• Differentiates AD pathology from primary tauopathies
• Useful for treatment stratification

Second-Generation Tau Tracers

• 18F-MK-6240, 18F-PI-2620
• Better specificity for 3R/4R tau (CBD/PSP)
• Under investigation for CBS/PSP differentiation

Amyloid PET

11C-PiB, 18F-Florbetapir, 18F-Florbetaben

• Identify CBS patients with AD co-pathology
• ~40-50% of CBS cases show amyloid positivity
• Important for diagnostic accuracy and trial enrollment
• Helps explain atypical presentations

Dopaminergic Imaging

DaT-SPECT (123I-FP-CIT, 123I-β-CIT)

• Demonstrates dopaminergic terminal loss
• Cannot differentiate CBS from PSP (both show loss)
• Helps differentiate from idiopathic PD
• Supports neurodegenerative parkinsonism diagnosis

18F-FDOPA PET

• Measures dopamine synthesis capacity
• Reduced in both CBS and PSP
• Limited utility for differential diagnosis

Advanced Imaging Techniques

Diffusion MRI

Diffusion Tensor Imaging (DTI)

• CBS: Asymmetric white matter tract involvement
• PSP: Symmetric involvement, superior cerebellar peduncle
• Fractional anisotropy reduction in specific tracts

Neurite Orientation Dispersion and Density Imaging (NODI)

• More specific for neuronal loss
• Emerging utility in CBS/PSP differentiation

Multi-model Diffusion Signatures

MR Spectroscopy

• Reduced N-acetylaspartate in affected regions
• Elevated choline reflecting membrane turnover
• Limited clinical utility currently

Network-Based Imaging

Resting-State fMRI

• Disrupted functional connectivity patterns
• Sensorimotor network involvement in both conditions
• Different connectivity signatures between CBS and PSP

Multimodal Imaging Approaches

Integrated Diagnostic Frameworks

Combining multiple imaging modalities improves diagnostic accuracy:

Clinical Application Algorithm

Research Applications

Clinical Trial Enrichment

• Imaging biomarkers select homogeneous patient populations
• Biomarker-defined subgroups for targeted therapies
• Outcome measures for treatment response

Disease Progression Markers

• Serial MRI for atrophy rates
• FDG-PET for metabolic progression
• Tau PET for pathological burden tracking

Cost and Accessibility Analysis

Comparative Costs of Imaging Modalities

| Modality | Approximate Cost (USD) | Accessibility | Diagnostic Utility Score |
|----------|----------------------|--------------|---------------------|
| Structural MRI | $500-1,500 | Moderate-High | High |
| FDG-PET | $2,000-4,000 | Moderate | High |
| Tau PET | $3,000-6,000 | Low-Moderate | High |
| Amyloid PET | $2,500-5,000 | Moderate | Moderate |
| DTI | $800-2,000 | Moderate | High |
| DaT-SPECT | $1,500-3,000 | Moderate | Moderate |
| Resting-state fMRI | $800-2,000 | Moderate | Moderate |

Cost-Effectiveness Considerations

• Structural MRI remains the first-line, most cost-effective imaging modality for CBS/PSP
• FDG-PET offers highest diagnostic value per cost for differential diagnosis
• Amyloid PET essential for identifying AD co-pathology in CBS patients (~40-50% of cases)
• Tau PET provides direct tau pathology visualization but at highest cost
• Combined multimodal approach maximizes diagnostic accuracy while optimizing costs

Clinical Implementation Recommendations

| Scenario | Recommended Imaging Sequence |
|----------|-------------------------|
| Initial evaluation | Structural MRI → FDG-PET (if needed) |
| AD co-pathology suspected | Add Amyloid PET |
| Research/clinical trials | Full multimodal including Tau PET |
| Resource-limited setting | MRI + clinical assessment |

Regulatory Status

FDA Clearance Status

| Modality | Status | Notes |
|----------|--------|-------|
| Structural MRI | FDA Cleared | Standard of care |
| FDG-PET | FDA Cleared | For dementia differential |
| Amyloid PET (PiB, Florbetapir, Florbetaben) | FDA Cleared | For amyloid detection |
| Tau PET (Flortaucipir) | FDA Cleared | For tau imaging |
| DaT-SPECT | FDA Cleared | For dopaminergic imaging |

CE Marking (Europe)

• All major PET tracers (FDG, amyloid, tau) have CE marking under EU IVDR
• DTI and advanced MRI sequences are CE marked on most scanners
• Commercial software packages for automated analysis received CE marking

Asian Regulatory Status

| Region | Modality | Status |
|--------|---------|--------|
| Japan (PMDA) | FDG-PET, Amyloid PET, Tau PET | Approved |
| China (NMPA) | FDG-PET, Amyloid PET | Approved |
| South Korea (KFDA) | FDG-PET, Amyloid PET, Tau PET | Approved |

• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

External Links

• [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
• [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)

Allen Brain Atlas Resources

• [Allen Brain Atlas - Gene Expression](https://human.brain-map.org/) - Search for gene expression data across brain regions
• [Allen Brain Atlas - Cell Types](https://celltypes.brain-map.org/) - Explore neuronal cell type taxonomy

References