Fetal ventriculomegaly (differential)

Last revised by Alexandra Stanislavsky on 27 Jul 2022

Fetal ventriculomegaly (ventricle width >10 mm) is an important finding in itself and it is also associated with other central nervous system abnormalities. For more information, see the main article fetal ventriculomegaly.

Differential diagnosis

Fetal ventriculomegaly can be thought of in terms of three categories:

  • obstructive
  • dysgenesis
  • destructive
Obstructive causes

This category encompasses enlargement of a structurally normal cerebral ventricle.

  • ventricles are typically smooth-walled
  • ventricle orientation is normal
  • cortex is intact, but compressed
  • the posterior fossa structures may be abnormal
    • if normal, consider aqueductal stenosis
  • the cavum septum pellucidi may be absent in severe obstructive ventriculomegaly
  • the falx is present

One should search for an obstructing lesion causing the hydrocephalus. 

Differentials include:

Dysgenesis causes

This category encompasses enlargement of a structurally abnormal cerebral ventricle:

  • ventricle shape and position is abnormal
  • ventricles are typically smooth-walled
  • the cavum septum pellucidi is abnormal
  • falx is often normal
  • the cerebral cortex is intact (with the exception of open lip schizencephaly)
  • other CNS abnormalities may be visible (e.g. fused frontal horns)

Differentials include:

Destructive causes

This category encompasses vascular events (infarcts) to the developing brain.

  • ventricle position is normal
  • the ventricle wall may be nodular from old hemorrhage
  • thinning/loss of cerebral cortex in a patchy asymmetric distribution
  • midline structures are normal
  • posterior fossa structures are normal
  • the falx is present

Differentials include:

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