By: Nour-Eldin Mohammed Neuroradiology Congenital Malformation of CNS

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)

Vielen Dank