Congenital Malformations Overview

(Left) Midline analysis using

sagittal T1WI MR shows

classic findings of Dandy

Walker spectrum with a large

posterior fossa cyst st, high

torcular ﬈, and a small,

upwardly rotated vermis ﬇.

There is also a significant

commissural anomaly with

only a small corpus callosum

remnant present ſt. The

rostrum and splenium are

absent. The anterior

commissure ﬊ is present and

appears normal. (Right) T2WI

in the same case shows that

the 4th ventricle is open

dorsally ﬇, contiguous with

the huge posterior fossa cyst.

(Left) Sagittal T1WI shows a

hypoplastic callosum rostrum

and splenium, plus a small

interhemispheric lipoma ﬇.

(Right) Sagittal T2WI shows a

very small posterior fossa with

a low-lying torcular st and an

elongated 4th ventricle ﬇

that lacks a fastigium. This

patient has a classic Chiari 2

malformation.

(Left) Midline analysis of a

sagittal T2WI shows a normalsized posterior fossa. The

cerebellar tonsils are pointed

ſt and displaced inferiorly 1

cm below the foramen

magnum. Note cord

hyperintensity ﬇, suggesting

a "presyrinx" state in this case

of Chiari 1 malformation.

(Right) Axial T2WI in the same

case shows the mass-like

thickening of the right medial

parietal gray matter and

distorted sulcal-gyral pattern

of cortical dysplasia.

Trauma, and Stroke

Brain: Pathology-Based Diagnoses: Malformations,

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