Posterior fossa arachnoid cyst

Case contributed by Dr Heba Mohamed


Weakness of the right side of the body since two days.

Patient Data

Age: 70 years
Gender: Female

Large extra-axial lesion of the posterior fossa with CSF-like density. No surrounding oedema or mass effect on the fourth ventricle. No solid nodules. No CT findings of cerebral vascular insufficiency. CT findings suggest a posterior fossa arachnoid cyst type 2b.

Case Discussion

Posterior fossa arachnoid cysts can be classified into four subgroups as follow:

  • 1a: midline inside the 4th ventricle treated by shunting or endoscopic fenestration
  • 1b: midline outside the 4th ventricle, treated by surgery
  • 2a: off-midline within the cerebellopontine angle treated by surgery f endoscopic fenestration
  • 2b: off-midline either retro-cerebellar or intracerebellar treated by surgery
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Case information

rID: 52405
Published: 7th Apr 2017
Last edited: 16th Jul 2018
Inclusion in quiz mode: Included

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