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
It is important to note that the current belief that olivopontocerebellar degeneration, Shy-Drager syndrome, and striatonigral degeneration are different manifestations of the same underlying disease, namely multiple systemic atrophy (MSA), is recent, and as such many older publications will describe these as separate entities 2,3.
For a discussion of epidemiology and pathology, please refer to: 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 MSA-P, parkinsonism is generally less prominent.
Radiographic features
MRI
There is disproportionate atrophy of the cerebellum and brainstem (especially olivary nuclei and middle cerebellar peduncle), with one study suggesting the rate of atrophy to be a diagnostic feature of MSA-C 5. This study found the following thresholds of decline to be diagnostic 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%
Additionally, there may be T2/FLAIR hyperintensities in certain locations 4.
T2/FLAIR: hyperintensities of the pontocerebellar tracts, middle cerebellar peduncles (middle cerebellar peduncle sign), pons (hot cross bun sign) 4