Cortico-basal Syndrome (CBS) presents significant diagnostic challenges due to phenotypic overlap with Progressive Supranuclear Palsy (PSP), Parkinson's disease, Frontotemporal Dementia, Alzheimer's disease, and Multiple System Atrophy (MSA). Accurate differentiation is critical for prognosis, genetic counseling, and therapeutic decision-making[1].
| Feature | CBS | PSP |
|---|---|---|
| Onset | Asymmetric | Symmetric |
| Cortical signs | Prominent (apraxia, alien limb) | Absent/minimal |
| Eye movements | Usually preserved initially | Vertical supranuclear gaze palsy |
| Postural instability | Late | Early (within 1 year) |
| Falls | Late (median 2-3 years) | Early (median 1 year) |
| MRI atrophy | Asymmetric frontoparietal | Midbrain "hummingbird" sign |
| FDG-PET | Asymmetric frontoparietal hypometabolism | Midbrain, thalamus, frontal hypometabolism |
Key discriminating features:
| Feature | CBS | Parkinson's Disease |
|---|---|---|
| Symmetry | Markedly asymmetric | Initially symmetric |
| Levodopa response | Poor | Good (initially) |
| Tremor | Less common | Common (resting) |
| Cortical signs | Present | Absent |
| Dementia | Early (1-2 years) | Late (>10 years) |
| Disease course | Rapid progression | Slow progression |
| Neuroimaging | Asymmetric cortical atrophy | Often normal |
Critical distinctions:
| Feature | CBS | bvFTD |
|---|---|---|
| Motor symptoms | Prominent early | Variable, often late |
| Parkinsonism | Present | Usually absent |
| Apraxia | Common | Uncommon |
| Language | Non-fluent aphasia common | Variable |
| Behavior | Often preserved initially | Early disinhibition/apathy |
| Motor imaging | Asymmetric frontoparietal | Often normal |
Overlap considerations:
| Feature | CBS | Alzheimer's Disease |
|---|---|---|
| Memory | Early preservation, late deficits | Early prominent deficits |
| Orientation | Early preserved | Early impaired |
| Motor signs | Early, prominent | Late (if at all) |
| Cortical signs | Early, prominent | Variable |
| MRI | Asymmetric frontoparietal | Posterior (temporal/parietal) |
| Amyloid PET | Usually negative | Usually positive |
Important considerations:
| Feature | CBS | MSA |
|---|---|---|
| Autonomic failure | Late, mild | Early, prominent |
| Cerebellar signs | Rare | Common (MSA-C) |
| Parkinsonism | Asymmetric, poor levodopa | Symmetric, poor levodopa |
| MRI | Asymmetric cortical | "Hot cross bun" sign, brainstem atrophy |
| DaTscan | Abnormal | Abnormal |
The standardized criteria require asymmetric presentation with at least one cortical sign AND one extrapyramidal sign[2]:
Core clinical features:
Cortical signs (≥1 required):
Extrapyramidal signs (≥1 required):
Supportive features:
| Condition | Key Finding |
|---|---|
| CBS | Asymmetric frontoparietal atrophy, "knife-edge" gyri, callosal atrophy |
| PSP | Midbrain atrophy ("hummingbird sign"), pontine "Maltese cross", superior cerebellar peduncle atrophy |
| PD | Usually normal, may show subtle nigral degeneration |
| MSA-P | Putaminal atrophy, "hot cross bun" sign |
| MSA-C | Cerebellar and brainstem atrophy |
| AD | Posterior temporal and parietal atrophy, hippocampal sclerosis |
| Condition | Pattern |
|---|---|
| CBS | Asymmetric frontoparietal hypometabolism, putaminal hypometabolism |
| PSP | Midbrain, frontal cortex, thalamus hypometabolism |
| PD | Posterior putamen (contralateral) hypometabolism |
| MSA | Cerebellar (MSA-C), putaminal (MSA-P) hypometabolism |
| AD | Posterior cingulate, temporoparietal hypometabolism |
pierotti2018
| Marker | CBS | PSP | PD | AD | MSA |
|---|---|---|---|---|---|
| t-tau | Normal-elevated | Normal-elevated | Normal | Elevated | Normal |
| p-tau | Normal | Normal | Normal | Elevated | Normal |
| NfL | Elevated | Elevated | Normal-mild | Normal-mild | Elevated |
| α-synuclein RT-QuIC | Usually negative | Usually negative | Usually positive | Negative | Usually positive |
| Marker | CBS | PSP | PD | AD |
|---|---|---|---|---|
| NfL | Elevated | Elevated | Normal-mild | Normal |
| p-tau217 | Normal | Normal | Normal | Elevated |
| p-tau181 | Normal | Normal | Normal | Elevated |
For uncertain cases:
Alexander et al. Corticobasal syndrome: diagnostic accuracy and utility. Neurology. 2014. ↩︎
Armstrong et al. Criteria for corticobasal degeneration: a consensus statement. Mov Disord. 2013. ↩︎