Purpose or Case Report: Neuronal migration and cortical organization takes place primarily during the second trimester and early third trimester. Therefore, detection of cortical malformations and migrational anomalies on a fetal MRI in a maturing brain is difficult and may not be evident in some cases, if performed early.
Familiarity with normal sulcation pattern in a fetus at various ages of gestation and a basic understanding of the embryogenesis of neuronal migration is essential to be able to make a diagnosis of these entities.

Goals of the exhibit
-Understand development of cerebral cortex and normal fetal MRI appearance at various stages of gestation.
- Using this knowledge, be able to recognize various cortical malformations in a fetus and provide a comprehensive diagnosis regarding etiology, whenever feasible or when the appearance is typical or when there are ancillary findings
- Avoid certain pitfalls and improve accuracy without overcalling or undercalling migrational anomalies in a fetal MRI

Outline of the exhibit
Embryology of neuronal migration (during second and third trimesters)
Normal sulcation pattern during mid and late trimesters
Etiology of neuronal migration and cortical malformations
-Multifactorial
- Infectious
- Genetic mutation/chromosomal
- Ischemic insult
- Metabolic disorders like Zellweger
Appearance of various migrational anomalies and cortical malformations in a fetal brain
Polymicrogyria – subtle and extensive forms, appearance during various stages of gestation, correlation with post-natal imaging, typical appearance in certain genetic mutations, TORCH infections etc
Schizencephaly – associations with absence of septum pellucidum and other abnormalities
Gray matter heterotopia – How to differentiate from subependymal nodules and hemorrhage?
Lissencephaly – How to identify a true lissencephaly/pachygyria in a developing brain with immature sulcal pattern?
Hemimegalencephaly, Microcephaly with simplified gyral pattern and other cortical malformations
Evolution of cortical malformations on imaging
-Comparison between early and late gestation fetal MRIs in the same patient when available
- Prenatal and post-natal MRI correlation of migrational anomalies, when available
Ancillary CNS and extra-CNS abnormalities identified in fetuses with migrational anomalies
Pitfalls and false positive/ false negative cases and how to avoid them.

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