Fetal Ventriculomegaly MRI

Step-by-step decision

Choose step by step as prompted; reaching an endpoint gives the management recommendation. You can go back a step or restart anytime.

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Full pathway

1. [Decision] Lateral ventricular atrial width (SMFM)
   Lateral ventricular atrial width (axial thalamic plane, inner-to-inner)? (Atrium ≥10 mm (axial at the thalamus/cavum septi pellucidi, measured inner edge) = ventriculomegaly. VM is a sign, not a diagnosis. Carefully assess associated anomalies (agenesis of the corpus callosum/Dandy-Walker/NTD/migration) + chromosomes (karyotype/microarray) + TORCH (CMV/toxoplasma); fetal MRI for parenchyma and associated CNS anomalies (moderate/severe or when ultrasound is limited). MRI measurements differ from ultrasound by about 2 mm. A dangling choroid plexus sign may be seen in severe cases.)
   • 10–12 mm (mild) → Mild (10–12 mm) · usually good prognosis
   • 13–15 mm (moderate) → Moderate (13–15 mm) · MRI + chromosomes
   • >15 mm (severe) → Severe (>15 mm) · comprehensive assessment
2. [End] Mild (10–12 mm) · usually good prognosis
   Mild VM (10–12 mm): isolated has a good prognosis (>90% normal neurodevelopment); still exclude associated anomalies/chromosomes/infection, fetal MRI for parenchyma, serial follow-up for progression. Isolated is a diagnosis of exclusion (cannot be fully confirmed prenatally).
3. [End] Moderate (13–15 mm) · MRI + chromosomes
   Moderate VM (13–15 mm): isolated about 75–93% normal; fetal MRI to assess parenchyma and associated CNS anomalies + karyotype/microarray + TORCH (CMV/toxoplasma) + genetic counseling; serial monitoring for progression.
4. [End] Severe (>15 mm) · comprehensive assessment
   Severe VM (>15 mm): usually obstructive/hydrocephalus, high risk of associated anomalies and poor outcome; fetal MRI for comprehensive assessment (aqueductal stenosis, ACC, posterior fossa, hemorrhage, migration) + karyotype/microarray + TORCH + multidisciplinary counseling; manage individually by cause and progression.

Source guidelines & references

• Fetal ventriculomegaly grading and management (SMFM; AJOG 2020)

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

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