Pediatric Arachnoid Cyst of Posterior Fossa

  • Etiology: Congenital splitting of arachnoid layer with accumulation of cerebrospinal fluid within this potential space
  • Imaging:
    — Normal inferior vermis
    — May elevate torcula
    — May erode calvarium
    — Cyst may extend to cerebellopontine angle wrapping around cerebellar hemisphere
  • DDX:
  • Complications:
  • Treatment:
  • Clinical:

Radiology Cases of Arachnoid Cyst of Posterior Fossa

CT of arachnoid cyst of the posterior fossa
Axial CT without contrast of the brain shows a cystic structure on the left side of the posterior fossa that is shifting the cerebellum, which is structurally normal, to the right. The fourth ventricle is compressed leading to a moderate amount of hydrocephalus.