Congenital Malformations Overview

Brain Anomaly Imaging Checklist

Anomaly Findings

Anomalies of Cerebral Cortex

Agyria/pachygyria Thick cortex, smooth inner margin, few shallow sulci

Polymicrogyria Thin undulating cortex, irregular inner margin

Cobblestone cortex Thick cortex, irregular inner margin, abnormal myelin

Focal cortical dysplasia Blurred gray-white junction, ± abnormal myelination

White Matter Abnormalities With Cortical Malformation

Polymicrogyria Enlarged perivascular spaces

Cobblestone cortex Delayed myelination, patchy hypomyelination

Congenital cytomegalovirus Deep layers of hypomyelination/gliosis

Focal cortical dysplasia Focal subcortical hypomyelination

Malformations Associated With Absent Septi Pellucidi

Septooptic dysplasia

Holoprosencephaly

Bilateral schizencephaly

Bilateral polymicrogyria

Rhombencephalosynapsis

Malformations with prolonged severe hydrocephalus

Classification for Malformation of Cortical Development

Mechanism Examples

Abnormal cellular proliferation Polymicrogyria; focal cortical dysplasia

Abnormal neuronal migration Lissencephaly I; lissencephaly II; heterotopia

Abnormal cortical organization Schizencephaly; cortical dysplasia (balloon cells)

hippocampal; always look to make sure that they are fully

folded and not too round.

Always look at the entire interhemispheric fissure (IHF); if the

cerebral hemispheres are continuous across the midline,

holoprosencephaly should be diagnosed. In severe

holoprosencephalies, the interhemispheric fissure is

completely absent, whereas in milder forms of

holoprosencephaly certain areas of the IHF will be absent

(anterior IHF in semilobar holoprosencephaly, central IHF in

syntelencephaly). Look at the septum pellucidum; absence of

the septum is seen in corpus callosum dysgenesis/agenesis,

septooptic dysplasia, and in some cases of schizencephaly or

bilateral polymicrogyria. While checking the septum, look at

the lateral ventricles to ensure that they are normal in size and

shape. Abnormally enlarged trigones and temporal horns are

often associated with callosal anomalies and pachygyria.

Enlarged frontal horns are often seen in bilateral frontal

polymicrogyria.

Don't forget to look carefully at the posterior fossa; anomalies

of the brainstem and cerebellum are commonly overlooked.

Make sure that the 4th ventricle and cerebellar vermis are

normally sized. In newborns, the vermis should extend from

the inferior colliculi to the obex, whereas infants and older

children should have a vermis that extends from the

intercollicular sulcus to the obex. Also, make sure you see

normal vermian fissures. If the fissuration of the vermis looks

abnormal, look at an axial or coronal image to make sure the

vermis is present; if the cerebellar hemispheres are

continuous without a vermis between them, make a diagnosis

of rhombencephalosynapsis. If the 4th ventricle has an

abnormal rectangular shape (with a horizontal superior

margin) with a narrow isthmus and small vermis, think about a

molar tooth malformation. To confirm this diagnosis, look for

the molar tooth sign of the lower midbrain, consisting of