Pediatric Blake Pouch Cyst

• Etiology: Failure of regression of Blake’s pouch due to non-perforation of Foramen of Magendie
• Imaging: Cystic dilation of fourth ventricle
• DDX: Dandy Walker Continuum
• Dandy Walker malformation
  — Retrocerebellar cyst connecting to dilated fourth ventricle
  — Inferior vermian agenesis
  — Mass effect: cerebellar hemispheres splayed out and rotated up
  — Enlarged posterior fossa
  — High tentorium and sinuses (lambdoid torcular inversion)
  — Associations: Corpus callosum agenesis, migrational (polymicrogyria, heterotopia), cephaloceles (occipital), hydrocephalus, hypoplasia or atrophy of cerebellum or brainstem
• Dandy Walker variant
  — Smaller retrocerebellar cyst
  — Milder fourth ventricle dilation
  — Milder inferior vermian agenesis or hypogenesis
  — Normal size or mildly enlarged posterior fossa
  — Similar associations
• Mega cisterna magna
  — Enlarged cisterna magna (subarachnoid space)
  — Normal fourth ventricle
  — Intact with or without atrophic vermis
  — Normal sized or mildly enlarged posterior fossa
• Blake pouch cyst
  — Cystic dilation of fourth ventricle
• Complications:
• Treatment:
• Clinical:

Radiology Cases of Blake Pouch Cyst