Presentation
Headaches.
Patient Data
Age: 35 years
Gender: Male
From the case:
Retrocerebellar arachnoid cyst
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Left retrocerebellar extra-axial cyst compressing and displacing anteriorly the left cerebellar hemisphere. It elicits an isosignal to the CSF on all sequences with no restricted diffusion.
Case Discussion
MRI features of a retrocerebellar extra-axial cyst of CSF signal most consistent with an arachnoid cyst.
The main differential diagnosis, in such case, is mega cisterna magna which usually extends to both sides of the falx cerebelli. The posterior dural folds are easily seen within the enlarged retrocerebellar space. No mass effect or compression of the adjacent cerebellar hemisphere.