Congenital Malformations Overview

(Left) Axial NECT scan in an

18-year-old man with seizures

shows a unilateral

schizencephalic cleft

extending from the pial

surface of the brain ﬈ to the

ventricle. Note the

characteristic cerebrospinal

fluid "nipple" ſt at the

ventricular margin. The cleft is

lined by thickened, dysplastic

gray matter ﬇. (Right) Axial

T2WI shows bilateral

schizencephalic clefts ſt lined

by dysplastic gray matter ﬇.

Note the abnormal cortical

veins ﬉ associated with the

clefts.

(Left) Axial T2WI MR allows

analysis of midline and shows

absent interhemispheric

fissure in frontal lobes (white

matter continuous across

midline ſt). This finding, plus

the absence of frontal horns,

gives the diagnosis of

holoprosencephaly. (Right)

Analysis of coronal images

shows a squared-off

appearance to the lateral

ventricles with inferiorly

pointed frontal horns ſt,

absent septum pellucidum ﬇,

and hypoplastic optic chiasm

﬉ characteristic of septooptic

dysplasia.

(Left) Midline analysis of

posterior fossa structures

shows an upwardly convex

superior 4th ventricle ﬇ and

a dysplastic-appearing vermis

ſt. (Right) Axial T2WI in the

same case shows the

elongated 4th ventricle st,

cleft vermis ﬇, and thickened,

horizontally oriented superior

cerebellar peduncles ſt

forming the classic molar

tooth sign of Joubert

syndrome.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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