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By:Nour-Eldin Mohammed
NeuroradiologyNeuroradiologyCongenital Malformation Congenital Malformation
of CNSof CNS
Callosal DysgenesisCallosal 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 DysgenesisCallosal 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 DysgenesisCallosal Dysgenesis
Radially arrayed gyri "point to" 3rd ventricle
Absent Cingulate Gyrus
Callosal DysgenesisCallosal Dysgenesis
Lateral ventricles are key to diagnosis:• Parallel (non-converging)• Widely separated
• Occipital horns often dilated (colpocephaly)• Pointed frontal horns
Callosal DysgenesisCallosal Dysgenesis
Coronal T2WI MRshows agenesis of the corpusCallosum
• trident shaped lateral ventricles
•vertical hippocampi (open
arrow),
•enlarged, "keyhole" shaped
temporal horns and Probst
bundles (curved arrow).
Callosal DysgenesisCallosal 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 DysgenesisCallosal Dysgenesis
Coronal T2WI MR in fetus shows trident shaped lateralventricles, agenesis of Cc
•"Probst bundle" (curved arrow)
• vertical hippocampus (arrow).
Differential Diagnosis of Callosal Dysgenesis Differential Diagnosis of Callosal Dysgenesis
Partial Absence of Callosal DysgenesisPartial Absence of Callosal Dysgenesis
Destruction of CC
Differential Diagnosis of Callosal Dysgenesis Differential Diagnosis of Callosal Dysgenesis
• Surgery (callosotomy),trauma (Acquired interhemispheric disconnection syndrome)• Hypoxic ischemic encephalopathy (HIE), infarcts• Metabolic
Differential Diagnosis of Callosal Dysgenesis Differential Diagnosis of Callosal Dysgenesis
Stretched Corpus Callosum (e.g.: Hydrocephalus)Stretched Corpus Callosum (e.g.: Hydrocephalus)
• Thinned CC but all parts present
• Severe hydrocephalus often present
LipomaLipoma
Definitions• Mass of mature non-neoplastic adipose tissue•CNS lipomas are congenital malformations, not trueneoplasm
LipomaLipomaGeneral 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
LipomaLipoma
(a small interhemispheric lipoma (arrows) above the corpus callosum, found incidentally at MR imaging in this patient with headache.
Sagittal Tl WI MR Sagittal Tl WI MR with fat-saturation
LipomaLipoma
Sagittal TlWI MR shows a well-circumscribed high signal lesion in the pineal region (arrow).The patient was asymptomatic.
Axial gross pathology shows
a quadrigeminal lipoma
(arrow)