fourth ventriculocoele

A fourth ventriculocoele is large posterior fossa cyst which remodels, thins and eventually erodes through the occipital bone to form an occipital encephalocoele.

It may be classified as part of the Dandy-Walker continuum, but this is controversial.

Related Radiopaedia articles

Malformations of the central nervous system

• malformations of cortical development
  • abnormal cell proliferation or apoptosis 
    • abnormal brain size
      • microcephaly
        • with normal to simplified cortical pattern
        • microcephaly with lissencephaly
        • microcephaly with extensive polymicrogyria
      • macrocephalies (megalencephaly/macrocephaly)
    • abnormal cell proliferation
      • non-neoplastic
        • cortical hamartomas of tuberous sclerosis 
        • hemimegalencephaly
        • focal cortical dysplasia (Type I and Type IIb)
          • Palmini classification (2004)
          • Barkovich classification (2005)
          • Blumcke classification (2011)
      • neoplastic
        • ganglioglioma
        • gangliocytoma
        • dysembryoplastic neuroepithelial tumor (DNET)
          • bright rim sign
    • abnormal neuronal migration
      • lissencephaly
        • lissencephaly type I: subcortical band heterotopia spectrum (band heterotopia): undermigration
        • lissencephaly type II (cobblestone complex)
      • heterotopia: ectopic migration
        • subependymal heterotopia
        • subcortical heterotopia (not including band heterotopia)
        • marginal glioneuronal heterotopia
    • abnormal cortical organization
      • mild malformations of cortical development (previously microdysgenesis)
      • polymicrogyria and schizencephaly
        • bilateral polymicrogyria syndromes
        • schizencephaly
      • focal cortical dysplasia (Type IIa)
  • not otherwise classified
    • malformations secondary to inborn errors of metabolism
      • mitochondrial and pyruvate metabolic disorders
      • peroxisomal disorders
    • other unclassified malformations
      • sublobar dysplasia
• midline abnormalities of the brain
  • absent septum pellucidum
  • cephaloceles
  • midline nasal region lesions
    • nasal dermoid
    • nasal glioma
    • nasal dermal sinus
  • cerebral hemispheres
    • holoprosencephaly/septo-optic dysplasia spectrum
      • septo-optic dysplasia
      • lobar holoprosencephaly
      • semilobar holoprosencephaly
      • alobar holoprosencephaly
      • middle interhemispheric variant/syntelencephaly
  • corpus callosum
    • corpus callosum agenesis /dysgenesis
      • racing car sign
  • intracranial lipoma
• malformations of the cerebellum
  • cerebellar hypoplasia
    • focal hypoplasia
    • generalized hypoplasia
      • with enlarged fourth ventricle
        • Dandy-Walker continuum
          • Dandy-Walker malformation
          • Dandy-Walker variant
            • isolated inferior vermian hypoplasia
          • Blake’s pouch cyst
          • fourth ventriculocoele
      • normal fourth ventricle
        • with normal pons
        • with small pons
          • normal foliation
            • pontocerebellar hypoplasias of Barth, types I and II
            • cerebellar hypoplasias, not otherwise specified
  • cerebellar dysplasia
    • focal dysplasia
      • isolated vermian dysplasia
        • molar tooth malformations including Joubert syndrome
        • rhombencephalosynapsis
      • isolated hemispheric dysplasia
        • focal cerebellar cortical dysplasias/heterotopia
        • Lhermitte-Duclos-Cowden syndrome
    • generalized dysplasia
      • congenital muscular dystrophies
      • cytomegalovirus
      • lissencephaly with RELN mutation
      • lissencephaly with agenesis of corpus callosum and cerebellar dysplasia
      • associated with diffuse cerebral polymicrogyria
      • diffusely abnormal foliation
• malformations of the brainstem