12. NEURONAL MIGRATION DISORDERS
• Development of the cerebral cortex happens in three stages:
proliferation,
migration
organization
• Schizencephaly and lissencephaly
• Schizencephaly is gray matter–lined, cerebrospinal fluid (CSF)–containing cleft
extending from the brain surface to the ventricle
• Lissencephaly is a disorder characterized by an absent or minimal sulcation pattern
36. VENTRICULOMEGALY
• Dilatation of the lateral ventricles >10 mm at the level of atria
at its widest part, perpendicular to the long axis of the ventricle
measured from inner wall to inner wall
• Mild 10-12 mm
• Moderate 13-15 mm
• Severe >15 mm
• near-field ventricle on the axial ventricular view is typically
poorly seen,if seen indicates osteogenesis imperfecta.
37.
38.
39.
40. HOLOPROSENCEPHALY
• Prosencephalon fails to divide into two distinct hemispheres
• Types: lobar
semilobar
alobar,
• Absence of the CSP is a charac-teristic feature of all three
subtypes
41. ALOBAR
• Failure of complete separation of two hemispheres.
• USG
• Monoventricle
• Fused thalami
• Absent corpus callosum
• Absent cavum septum pellucidum
• Absence of 3rd ventricle
• Middle and anterior cerebral arteries replaced by tangled branches of internal carotid and
basilar vessels.
• Severe facial malformations.
43. SEMILOBAR
• interhemispheric fissure is present posteriorly but absent
anteriorly, while the cerebral ventricles are partially fused
anteriorly but separated posteri-orly
44. LOBAR
• midline falx is intact and present, the CSP are absent, and there is partial
fusion of the frontal horns
• Septo-optic dys-plasia is main differential diagnosis.
