ANOMALIES

HOLOPROSENCEPHALY

0Absence of brain tissue in the midline0Fusion of lateral ventricles to form a single chamber0Eye field area fails to separate

Schizencephaly

0Formation of clefts in cerebral hemisphere0Loss of brain tissue may also occur

Defects in ossification of skull bones

0Most common is that of sq.part of occipital bone0 If opening is small, only the herniation of meninges

takes place(Meningocele)0 If large , cranial tissue may also be

involved(Meningoencephalocele)0 If ventricles also

involved(Meningohydroencephalocele)

Exencephaly

0Failure of closure of neural folds in cephalic region0Vault of skull is absent0Nervous tissue is exposed, degenerates and becomes

necrotic---anencephaly0Swallowing reflex absent— Hydramnios present

Craniorachischisis

0 If NTD(Failure of closure) extends upto the spinal cord—craniorachischisis----Anencephaly occurs

Hydrocephalus

0Abn.accumulation of CSF in ventricles0Most common cause is the obstruction in aqueduct of

Sylvius0Pressure on brain and skull

bones---opening/widening of skull---large sized skull0Sometimes thinning of brain tissue and bones also

occurs

Arnold-Chiari Syndrome

0Caudal displacement and herniation of cerebellar structures

Microencephaly

0Underdevelopment of brain and overlying skull0CAUSES:0Fetal insults by0DRUGS0RADIATION0TERATOGENS0 INFECTIONS(Rubella,Toxoplasmosis,Cytomegalovirus

)0Maternal alcohol abuse

ABSENCE OF CORPUS CALLOSUM

0Without much functional disturbence

ABSENCE OF CEREBELLUM

0Only a little difficulty in coordination