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.
One or all segments of CC absent
(if partial, body remains)
Radially arrayed gyri "point to" 3rd ventricle
Absent Cingulate Gyrus
Lateral ventricles are key to diagnosis:
• Parallel (non-converging)
• Widely separated
• Occipital horns often dilated (colpocephaly)
• Pointed frontal horns
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.
Partial Absence of Callosal Dysgenesis
Destruction of CC
• Surgery (callosotomy),trauma (Acquired interhemispheric disconnection syndrome)
• Hypoxic ischemic encephalopathy (HIE), infarcts
Stretched Corpus Callosum (e.g.: Hydrocephalus)
• Thinned CC but all parts present
• Severe hydrocephalus often present
• 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)
• Cerebellopontine angle (may extend into lAC, vestibule)
• Uncommon: Jugular foramen, foramen magnum
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.
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)