Middle cerebellar peduncle sign
Imaging
biomarkers in Parkinson’s disease and Parkinsonian syndromes: current and emerging concepts. MRI of a patient with a clinical diagnosis of Multiple System Atrophy-C. a Axial proton density sequence at the level of the pons demonstrates cruciform pontine T2 hyperintensity consistent with the ‘hot cross bun’ sign secondary to selective vulnerability of the pontocerebellar tract in Multiple System Atrophy-C. Disproportionate atrophy of the pons and partially visualized cerebellar hemispheres is also evident. b Axial FLAIR sequence with cruciform T2 hyperintensity within the pons and middle cerebellar peduncles (i.e., ‘Middle Cerebellar Peduncle sign’) with marked atrophy. Cerebellar hemispheric and vermian atrophy is also seen with ex vacuo dilatation of the fourth ventricle. c Sagittal T1 sequence showing marked atrophy of the brainstem and cerebellar vermis
The middle cerebellar peduncle (MCP) sign is a feature of a number of conditions, particularly neurodegenerative diseases, and most commonly associated with fragile X-associated tremor/ataxia syndrome (FXTAS) although many other conditions are recognized.
It represents high T2 signal in the middle cerebellar peduncles, which contain the frontocerebellar tracts (connecting to orbitofrontal and dorsolateral prefrontal cortex) .
The MCP sign is seen in a number of conditions including :
- chronic liver disease
- adrenoleukodystrophy
- Behcet disease
- chasing the dragon (heroin inhalation toxic leukoencephalopathy)
- cyclosporin-A encephalopathy
- demyelination
- infective
- HIV encephalopathy
- JC virus granule cell neuronopathy
- Zika virus encephalitis in adults
- neurodegenerative
- CARASIL: with involvement of pons; known as the arc sign
- recessive ataxia
- spinocerebellar ataxia
- multiple system atrophy - cerebellar (MSA-C): atrophy is usually the striking abnormality
- fragile X-associated tremor/ataxia syndrome (FXTAS)
- vascular
- bilateral anterior inferior cerebellar artery infarction
- posterior reversible encephalopathy syndrome (PRES)
- Wallerian degeneration secondary to pontine stroke
It can of course also be encountered 'randomly' in diseases that have no particular regional predilection (e.g. stroke, tumor).
