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.
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
The imaging biomarkers show generalizable utility across populations, though population-specific normative databases improve diagnostic accuracy.
- 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
- 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
| Region | CBS | PSP |
|--------|-----|-----|
| Motor cortex | Asymmetric, severe | Symmetric, moderate |
| Parietal lobe | Prominent atrophy | Less affected |
| Brainstem | Less affected | Midbrain prominent |
| Cerebellum | Variable | Superior peduncle |
- Cortical thickness: Reduced in CBS, helps quantify atrophy
- Subcortical volumes: Basal ganglia, thalamus measurements
- Diffusion tensor imaging: White matter tract integrity
- 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
- Brainstem: Midbrain prominent
- Frontal cortex: Particularly superior frontal
- Globus pallidus: Characteristic finding
- Thalamus: Dorsomedial nucleus
- Cerebellar: Less prominent than brainstem
- 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
- 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
- 18F-MK-6240, 18F-PI-2620
- Better specificity for 3R/4R tau (CBD/PSP)
- Under investigation for CBS/PSP differentiation
- 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
- Demonstrates dopaminergic terminal loss
- Cannot differentiate CBS from PSP (both show loss)
- Helps differentiate from idiopathic PD
- Supports neurodegenerative parkinsonism diagnosis
- Measures dopamine synthesis capacity
- Reduced in both CBS and PSP
- Limited utility for differential diagnosis
- 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
Recent research (2026) has identified multi-model diffusion MRI signatures that can distinguish atypical Parkinsonian disorders with high accuracy.
- Reduced N-acetylaspartate in affected regions
- Elevated choline reflecting membrane turnover
- Limited clinical utility currently
- Disrupted functional connectivity patterns
- Sensorimotor network involvement in both conditions
- Different connectivity signatures between CBS and PSP
Combining multiple imaging modalities improves diagnostic accuracy:
- Structural MRI + FDG-PET: ~90% accuracy for CBS vs PSP
- MRI + Amyloid PET: Identifies CBS-AD subtype
- DTI + FDG-PET: Complementary information
- Tau PET + Amyloid PET: Complete proteinopathy profiling
- Structural MRI: First-line, assess atrophy patterns
- FDG-PET: If diagnosis uncertain after MRI
- Amyloid PET: If AD pathology suspected
- Tau PET: If available, for tauopathy subtyping
- Dopaminergic imaging: If PD needs exclusion
- Imaging biomarkers select homogeneous patient populations
- Biomarker-defined subgroups for targeted therapies
- Outcome measures for treatment response
- Serial MRI for atrophy rates
- FDG-PET for metabolic progression
- Tau PET for pathological burden tracking
¶ Cost and Accessibility Analysis
| 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 |
- 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
| 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 |
| 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 |
- 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
| 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 |