Fetal Malformation of Cortical Development (MCD) MRI

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Full pathway

1. [Decision] Sulcation/cortical pattern (against gestation)
   Sulcation / cortical pattern (against gestation)? (MCD by the Barkovich classification (abnormal proliferation/migration/post-migrational organization). Key fetal MRI feature = sulcation timing (against gestation). Hard to assess <20–24 weeks, recheck at 24–34 weeks (mild sulcation delay may normalize), confirm on postnatal MRI. With abnormal sulcation, also check CC/posterior fossa/calcification/head circumference.)
   • Delayed/absent sulcation, smooth brain surface, thick cortex → Lissencephaly-pachygyria spectrum
   • Early/abnormal sulci, irregular cortical surface, irregular ventricular wall → Polymicrogyria (PMG)
   • Gray-matter-lined cleft (ependyma to pia) → Schizencephaly
   • Periventricular/band gray-matter nodules (heterotopia) → Gray-matter heterotopia
2. [End] Lissencephaly-pachygyria spectrum
   Lissencephaly-pachygyria spectrum (smooth brain + thick cortex, microlissencephaly when with microcephaly): migration disorder; check associated (CC dysgenesis, brainstem-cerebellar hypoplasia suggesting tubulinopathy); karyotype/microarray + exome (lissencephaly diagnostic yield near 100%; DCX/LIS1/tubulin); poor prognosis (severe epilepsy/developmental delay) + genetic counselling.
3. [End] Polymicrogyria (PMG)
   Polymicrogyria (PMG): early/abnormal sulci, irregular cortical surface and ventricular wall, abnormal Sylvian fissure; check CMV (a common cause) + chromosomal microarray + exome (~50% yield); may be with microcephaly or megalencephaly; prognosis follows extent (bilateral perisylvian PMG → epilepsy/motor-speech impairment) + counselling.
4. [End] Schizencephaly
   Schizencephaly: a gray-matter-lined cleft from ependyma to pia (open/closed lip); often with septum pellucidum absence/septo-optic dysplasia; check COL4A1, CMV; prognosis follows uni/bilateral and lip type (closed-lip unilateral is better); confirm on postnatal MRI + genetic assessment.
5. [End] Gray-matter heterotopia
   Gray-matter heterotopia (periventricular nodular PVNH / band double-cortex): fetal MRI shows ventricular-wall nodules or band gray matter (subtle ones may be missed); PVNH mostly FLNA (X-linked), band mostly DCX; karyotype/microarray + exome + family history; prognosis follows extent (focal may be epilepsy only). Confirm on postnatal MRI.

Source guidelines & references

• Fetal malformation of cortical development MRI diagnosis (Barkovich classification; Brain 2025 review)

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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