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 : 40-50% interhemispheric fissure (over corpus callosum; may extend into lateral ventricles, choroid plexus) 15-20% suprasellar(attached to infundibulum, hypothalamus) 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 well-circumscribed high signal lesion in the pineal region (arrow).The patient was asymptomatic. Axial gross pathology shows a quadrigeminal lipoma (arrow)