Neuroradiology
Congenital Malformation
of CNS
By:
Nour-Eldin Mohammed
Callosal Dysgenesis
Definitions:
One or all segments of CC absent
(if partial, body remains)
CC segments front to back:
• Lamina rostralis (unmyelinated)
• Rostrum (myelinated)
• Genu
• Body
• Splenium
Callosal Dysgenesis
• General Features:
• Axial: Parallel lateral ventricles
• Coronal: "Trident" anterior horns
resemble "viking helmet" or "moose
head“
• Location: Midline anomaly
• Size: CC remnants vary in size, shape
, Remnant may be paper thin or
bulbous
Callosal Dysgenesis
Radially arrayed gyri "point to"
3rd ventricle
Absent Cingulate Gyrus
Callosal Dysgenesis
Lateral ventricles are key to
diagnosis:
• Parallel (non-converging)
• Widely separated
• Occipital horns often dilated
(colpocephaly)
• Pointed frontal horns
Callosal Dysgenesis
Coronal T2WI MR
shows agenesis of the corpus
Callosum
• trident shaped lateral ventricles
•vertical hippocampi (open
arrow),
•enlarged, "keyhole" shaped
temporal horns and Probst
bundles (curved arrow).
Callosal Dysgenesis
Axial NECT with widened "windows" shows
colpocephaly, calcified (arrow) midline lipoma
that extends through choroid fissures into
lateral ventricles (open arrows).
Axial TlWI MR shows parallel
ventricles, colpocephaly, and a
midline lipoma. Note lipoma (arrow)
protruding into the lateral ventricles.
Callosal Dysgenesis
Coronal T2WI MR in fetus
shows trident shaped lateral
ventricles, agenesis of Cc
•"Probst bundle" (curved arrow)
• vertical hippocampus (arrow).
Differential Diagnosis of Callosal Dysgenesis
Partial Absence of Callosal Dysgenesis
Differential Diagnosis of Callosal Dysgenesis
Destruction of CC
• Surgery (callosotomy),trauma
(Acquired
interhemispheric disconnection syndrome)
• Hypoxic ischemic encephalopathy (HIE), infarcts
• Metabolic
Differential Diagnosis of Callosal Dysgenesis
Stretched Corpus Callosum (e.g.: Hydrocephalus)
• Thinned CC but all
parts present
• Severe hydrocephalus
often present
Lipoma
Definitions
• Mass of mature non-neoplastic adipose
tissue
•CNS lipomas are congenital
malformations, not true
neoplasm
Lipoma
General Features
• Best diagnostic clue: Well-delineated lobulated
extra-axial mass with fat attenuation/intensity
• Location : Midline location common
80% supratentorial :
1.
40-50% interhemispheric fissure (over corpus
callosum; may extend into lateral ventricles,
choroid plexus)
2. 15-20% suprasellar (attached to infundibulum,
hypothalamus)
3. 10-15% pineal region (usually attached to
tectum)
20% infratentorial
• Cerebellopontine angle (may extend into lAC,
vestibule)
• Uncommon: Jugular foramen, foramen magnum
Lipoma
Sagittal Tl WI MR
Sagittal Tl WI MR with fat-saturation
(a small interhemispheric lipoma (arrows) above the corpus callosum, found
incidentally at MR imaging in this patient with headache.
Lipoma
Sagittal TlWI MR shows a wellcircumscribed high signal lesion in the
pineal region (arrow).The patient was
asymptomatic.
Axial gross pathology shows
a quadrigeminal lipoma
(arrow)