Multiple system atrophy cerebellar type (MSA-C), previously known as olivopontocerebellar degeneration, is a neurodegenerative disease, and one of the clinical phenotypes of multiple systemic atrophy (MSA).
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Terminology
The prevailing thought is that that olivopontocerebellar degeneration, Shy-Drager syndrome and striatonigral degeneration are different manifestations of the same underlying disease, namely multiple systemic atrophy (MSA). However, many older publications will describe these as separate entities 2,3.
For a discussion of epidemiology, pathology and diagnosis see: multiple systemic atrophy (MSA).
Clinical presentation
MSA-C presents predominantly with cerebellar and brainstem symptoms and signs. Typically ataxia and bulbar dysfunction are pronounced. Autonomic dysfunction is also common.
Unlike the other clinical phenotype (MSA-P), parkinsonism is less evident.
Radiographic features
MRI is the imaging of choice in patients suspected of MSA. A diagnosis is made with a combination of clinical and MRI findings, although a negative MRI does not exclude MSA 6. Significant overlap of imaging findings exists between MSA-C and MSA-P 6.
MRI
Disproportionate atrophy of the cerebellum and brainstem (especially olivary nuclei and middle cerebellar peduncle), with one study suggesting the rate of atrophy to be characteristic of MSA-C at the following thresholds 5:
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rate of atrophy in measuring the anterior–posterior pons: -0.87 mm/year (highly specific but not very sensitive)
a rate of -0.4 mm/year had a sensitivity of 92% and a specificity of 87%
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rate of atrophy in measuring transverse middle cerebellar peduncle diameter: -0.84 mm/year (highly specific but not very sensitive)
a rate of -0.5 mm/year had a sensitivity of 85% and specificity 79%
Abnormal T2/FLAIR hyperintensities of the pontocerebellar tracts, middle cerebellar peduncles (middle cerebellar peduncle sign), pons (hot cross bun sign) 4
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