Retrocerebellar arachnoid cyst

Case contributed by Dr Heba Abdelmonem



Patient Data

Age: 7 years
Gender: Male


A left cerebellar extra-axial lesion with CSF signal that exerts a mass effect upon the left cerebellar hemisphere. Findings that are consistent with a retro-cerebellar Arachnoid cyst.

Case Discussion

The major differential diagnosis, in this case, is mega cisterna magna with the following points helping in differentiation:

  1. mega cisterna magna extends to both sides of the falx cerebelli, encasing it, with the free falx cerebelli and posterior dural folds easily seen within the enlarged retrocerebellar space
  2. mega cisterna magna lacks a compression or a mass effect upon the cerebellum
  3. the presence of signal void vascular structure within or next to the CSF space favors mega cisterna magna
  4. scalloping of the adjacent bone favors the diagnosis of an arachnoid cyst
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Case information

rID: 71871
Published: 16th Nov 2019
Last edited: 19th Nov 2019
Inclusion in quiz mode: Included
Institution: Zagazig University Hospital

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