Fetal Ventriculomegaly

Ventriculomegaly

The atrium of the lateral ventricle (measured at the level of the glomus of the choroid plexus, across the atria) is normally <10 mm. Ventriculomegaly is diagnosed when the atrial diameter is ≥10 mm.

Classification (based on atrial width)

• Mild (borderline): 10–12 mm
• Moderate: 13–15 mm
• Severe: >15 mm (sometimes called hydrocephalus when progressive and associated with increased head size/intracranial pressure)

Severe Ventriculomegaly

Figer

Ultrasound report line (Findings):Each Lateral ventricles are markedly dilated measuring >15 mm at the atrial level, with ballooning of the ventricular atria, consistent with severe ventriculomegaly.
Right atria:15.0 mm
Left atria:17.5 mm
Conclusion: Severe Ventriculomegaly
Recommendation: Detailed fetal neurosonography and anomaly scan to assess associated CNS and extra-CNS anomalies.
Consider fetal MRI for further evaluation of brain parenchyma and associated anomalies.
Recommend counseling and evaluation for possible chromosomal, genetic, or TORCH infectious etiologies.

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Etiology / Causes

Ventriculomegaly can be isolated or associated with other abnormalities:

1. Obstructive causes
   • Aqueductal stenosis
   • Neural tube defects (spina bifida, encephalocele)
   • Masses (tumors, hemorrhage, arachnoid cyst)
2. Non-obstructive causes
   • Chromosomal abnormalities (e.g., Trisomy 21, 18, 13)
   • Congenital infections (CMV, toxoplasmosis, Zika virus)
   • Cortical malformations (agenesis of corpus callosum, holoprosencephaly, lissencephaly)
   • Brain atrophy from ischemic/hemorrhagic injury

Sonographic Features

• Lateral ventricle atrium >10 mm, measured in axial plane at level of thalami and cavum septi pellucidi.
• Dangling choroid plexus sign (choroid plexus appears to “hang” within enlarged ventricle).
• Assess for associated findings:
  • Intracranial anomalies (corpus callosum agenesis, Dandy–Walker malformation)
  • Extracranial anomalies
  • Fetal growth restriction
  • Signs of infection (calcifications, microcephaly)

Prognosis

• Isolated mild ventriculomegaly (10–12 mm): ~80–90% have normal neurodevelopmental outcome.
• Moderate (13–15 mm): Outcome depends on progression and associated anomalies; ~60–70% normal if isolated.
• Severe (>15 mm): High risk of neurodevelopmental impairment, motor/cognitive deficits, or death.

Evaluation / Work-up

• Detailed fetal neurosonography (evaluate for structural CNS malformations).
• Fetal MRI (to assess cortical and midline structures).
• Genetic testing (amniocentesis with karyotype and microarray).
• TORCH screening for intrauterine infections.
• Serial ultrasounds to monitor progression.

Evaluation / Work-up

• Detailed fetal neurosonography (evaluate for structural CNS malformations).
• Fetal MRI (to assess cortical and midline structures).
• Genetic testing (amniocentesis with karyotype and microarray).
• TORCH screening for intrauterine infections.
• Serial ultrasounds to monitor progression.

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