Table 6.
Summary on characteristic MRI patterns for the differential diagnosis of neurodegenerative parkinsonism
| PD | MSA(-P) | PSP | |
|---|---|---|---|
| cMRI | |||
| Normal | ++ | –/+ | –/+ |
| Putaminal atrophy | – | ++/+++ | ++ |
| Putaminal hyperintense rima | + | ++ | + |
| Putaminal hypointensity on T2a | – | ++ | – |
| Atrophy of pons and vermis cerebellaris | – | ++ | + |
| Signal changes in the pons (hot cross bun sign) or MCPsa | – | ++ | – |
| Midbrain atrophy Mickey mouse sign and king-penguin silhouette |
– | – | ++ |
| MRI planimetry | |||
| Midbrain diameter | – | + | ++/+++b |
| Decreased md/pd ratio | – | + | +++ |
| Decreased ma/pa ratio | – | + | +++ |
| Increased MRPI | + | – | +++ |
| Diffusion imaging | |||
| Increased putaminal diffusivity | – | +++ | ++ |
| Increased diffusivity of MCP | + | +++ | + |
| Increased diffusivity of SCP | – | – | +++ |
| Iron-sensitive sequences | |||
| Increased putaminal iron load (e.g. putaminal hypointensity on T2* and SWI)c | + | +++d | ++ |
–, <20%; +, 20–50%; ++, 50–70%; +++, 70–90%; ++++, >90%. Signal changes (hyper- and hypointensities) refer to T2-weighted sequences. md/pd ratio = ratio of midsagittal midbrain to pons diameter by placing midsagittal elliptical ROIs. ma/pa ratio = ratio of midsagittal midbrain area to pons area. MRPI = MR-Parkinsonism index = (area pons/area midbrain) × (width MCP/width SCP)
cMRI conventional magnetic resonance imaging with routine sequences, T tesla, PD Parkinson’s disease, MSA multiple system atrophy, MSA-P parkinsonian variant of MSA, PSP progressive supranuclear palsy, MCP middle cerebellar peduncle, MRPI MR Parkinsonism Index, SCP superior cerebellar peduncle, ROI region of interest, SWI susceptibility-weighted imaging
aAt 1.5 T
bDepending on the assessment (for further details see text)
cDepending on the sequence used to measure iron load (for further details see text)
dTypically iron deposition in lower outer part of putamen