Fetal Neuroscience & Advanced Brain Imaging

Clinical Applications in Maternal–Fetal Medicine

Why Fetal Brain Imaging Matters

• CNS anomalies affect 1–3 per 1,000 births
• May alter delivery planning and counseling
• Imaging limitations require honest disclosure

Normal Brain Development Timeline

• 10–18 weeks: neuronal migration begins
• 20–24 weeks: sulcation commences
• 28–32 weeks: rapid cortical maturation

Ultrasound vs MRI: Complementary Roles

• Ultrasound: first-line, real-time, screening
• MRI: problem-solving, soft tissue detail
• Neither modality replaces postnatal assessment

Advanced Neurosonography Principles

• Transvaginal improves posterior fossa visualization
• Multiple planes reduce false positives
• Maternal habitus limits diagnostic confidence

What Fetal MRI Adds

• Overcomes acoustic shadowing
• Superior gray-white differentiation
• Associated with 20–50% diagnostic refinement

Optimal Timing for Fetal MRI

• Sulcation visible after 22 weeks
• Myelination assessment after 28 weeks
• Earlier imaging may require repeat study

MRI Sequences: Clinician-Level Overview

• T2: anatomic detail, CSF bright
• T1: hemorrhage, calcification detection
• DWI: acute ischemia, abscess characterization

Imaging Artifacts & Pitfalls

• Fetal motion degrades MRI quality
• Pseudomasses from partial volume averaging
• Biometry errors exaggerate mild ventriculomegaly

Ventriculomegaly Beyond Measurements

• Clue: asymmetry suggests obstruction
• Consider: infection, hemorrhage, aqueductal stenosis
• Limitation: isolated mild cases have variable outcomes

Corpus Callosum Abnormalities

• Clue: colpocephaly, high-riding third ventricle
• Consider: partial vs complete agenesis
• Limitation: prognosis depends on syndromic associations

Posterior Fossa Spectrum

• Clue: vermian hypoplasia, enlarged cisterna magna
• Consider: Blake pouch cyst, Dandy-Walker malformation
• Limitation: vermis matures late; avoid early labeling

Cortical Malformations

• Clue: abnormal sulcation pattern after 24 weeks
• Consider: lissencephaly, polymicrogyria, schizencephaly
• Limitation: subtle findings may emerge postnatally

Intracranial Hemorrhage

• Clue: T1 hyperintensity, mass effect
• Consider: alloimmune thrombocytopenia, vascular anomaly
• Limitation: cannot reliably predict neurodevelopmental impact

Ischemic & Infectious Injury Patterns

• Clue: DWI restriction, periventricular calcification
• Consider: CMV, Zika, arterial infarction
• Limitation: timing of insult difficult to determine

Imaging to Prognosis: Appropriate Limits

• Imaging findings raise concern, not destiny
• Isolated findings differ from syndromic patterns
• Postnatal assessment remains essential

Counseling Language for Families

• "This finding is associated with increased risk"
• "We cannot predict individual outcomes with certainty"
• "Serial imaging helps, but does not eliminate uncertainty"

Role of Serial Imaging

• May clarify evolution vs stability
• Interval change informs differential diagnosis
• Repeat studies do not guarantee prognostic clarity

Multidisciplinary Decision Making

• Radiology, genetics, neonatology, neurosurgery
• Family values central to care planning
• Team expertise reduces diagnostic overconfidence

Acknowledging Diagnostic Uncertainty

• Prenatal imaging has inherent resolution limits
• Honest acknowledgment builds trust
• Uncertainty is not failure of care

Key Takeaways

• Advanced imaging refines, does not define outcomes
• Probabilistic language protects families from false certainty
• Clinical humility improves shared decision making