Obstetrics

Absent cisterna magna4th ventricle through foramen magnumAssociated with Spina BifidaBanana- cerebellum shapeLemon- cranial frontal bossing

Absent cranial vaultAbsent cerebral hemispheres
bulging eyesmacroglossiashort neckpolyhydramnios

Protrusion of intracranial contests through defect of skullm/c occipital
Associated with:HydrocephalusSpina bifidapolyhydramniosMeckel Grubel Syndrome

Exagerrated hyperextension of headcervical spina bifidaspinal lordosisencephalocele

CSF accumulated in the ventricles. Obstruction and increased pressureClassifications: Aqueductal Stenosis Communicating Dandy Walker idiopathic

Enlargement of 3rd and lateral ventricles caused by obstruction of aqueduct of sylvius (connects 3rd and 4th ventricles)

Dilation of ventricles without enlargement of craniumu/s: compression of choroid plexus atria >1cm

"Water, No Brain"Total absence of cerebral hemispheresOccluded ICASkull presentu/s: macrocephalypolyhydramnios

Midline face deformitiesFailure of forebrain to divide into cerebral hemispheresAlobar: large single ventricleSemilobar: occipital lobe present; assoc cleft lipLobar: absent corpus callosum +CSP. Proboscis and cyclopia

Cystic areas within cerebral parenchymahydranencephaly-most severe form

4th ventricle is obstructed and dilated.Large cisterna magnacerebellar vermis is presentu/s: large midline cystic structure in posterior fossa

Failure of development of connection b/w cerebral hemispheres.Absent CSPenlarged occipital horn3rd ventricle enlarged

Abnormal clefts in cerebral hemispheres in primary fissures.Brain splits into anterior and posterior parts

Migration of neurons from germinal matrix to surface of brain.Lacks normal sulci and gyri= appears smooth

Anomalies: associated with Trisomy 18No anomalies: normal variant, resolve by 25 weeks