Neurosurgery notes/Paediatrics/Developmental abnormalities/Intracranial Anomalies/Posterior Fossa Cystic Malformations/Dandy-Walker variant

Dandy-Walker variant

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4th ventricle size
enlarged
Status
Done
Communication between 4th and cisterna magna
Files & media
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Hydrocephalus
Image explain
Axial T1-weighted magnetic resonance image showing Dandy-Walker variant with a fourth ventricle communicating with a retrocerebellar cyst (white arrow), absence of the inferior vermis, absence of the corpus callosum (black arrow), and lissencephaly.
Intrathecal contrast CT
Communicates with ventricles
Inferior Vermis
Hypoplasia/agenesis
Mass effect on the cerebellar hemisphere
No
Occipital bone scalloping
Position of choroid plexus
absent
Vermis remnant
cerebellar hemispheres
post fossa size
Normal

Aka

  • Isolated inferior vermian hypoplasia

Definition

  • Vermian hypoplasia
    • partial absence of the inferior portion of the cerebellar vermis
  • Normal sized
    • posterior fossa
    • 4th ventricle

Presentation

  • Mild functional deficits in fine motor activity and receptive language may be present.
  • Inferior vermian hypoplasia in isolation has no recurrence risk;

Evaluation

Imaging
  • Mid sagittal view: partial absence of the inferior vermis
  • Normal size and shape 
    • Superior vermis
    • cerebellar hemispheres,
    • Fourth ventricle,
    • posterior fossa
      •  
partial absence of the inferior vermis (arrow) and apparent but not true enlargement of the fourth ventricle
partial absence of the inferior vermis (arrow) and apparent but not true enlargement of the fourth ventricle
 
Sagittal T1-weighted MRI shows agenesis of the corpus callosum and a hypoplastic inferior vermis in a 13-year-old girl with thoracal scoliosis and Dandy-Walker variant. 4th ventricle is slightly enlarged, but the posterior fossa typically is normal in size.
Sagittal T1-weighted MRI shows agenesis of the corpus callosum and a hypoplastic inferior vermis in a 13-year-old girl with thoracal scoliosis and Dandy-Walker variant.
4th ventricle is slightly enlarged, but the posterior fossa typically is normal in size.
Prenatal diagnosis
  • Can be done after 18-20 wks gestation using MRI as U/S is not reliable (U/S: high false positive rates 30%)
    • Before 18 weeks gestation, incomplete caudal growth of the inferior vermis over the fourth ventricle may be physiologic
Outcome
  • 75% of patients have a favourable outcome