neo head (neural tube defects) pt 2

Arnold-Chiari Malformation is associated with -

spina bifida

Spina bifida pulls -

cerebellum and brainstem toward the spinal cord

Arnold-Chiari can cause -

• secondary hydrocephalus

• defect in calvarium and spinal column

Arnold Chiari malformation causes displacement of -

• 4th ventricle

• inferior cerebellum through the foramen magnum

Type 1 of Arnold-Chiari -

caudal displacement of the cerebellum only

Type II of Arnold-Chiari -

• most common

• Associated with meningomyelocele

Type III of Arnold-Chiari -

• Enchephalomeningocele containing cerebellum, 4th ventricle and medulla

Type VI of Arnold- Chiari -

• cerebellar hypoplasia

Agenesis of the corpus callosum may be -

isolated

agenesis of corpus callosum may be associated with -

hydrocephalus and Arnold-Chiari

Glial sling (in agenesis of CC)-

neural cells that gave a connective tissue supporting function in the CNS

Complete absence of corpus callosum -

• narrow and separated frontal horns

• widening of occipital horns

• widening of 3rd ventricle

Dandy-Walker malformation -

4th ventricle cystic formation

• causing secondary dilatation of the 3rd and lateral ventricles

In dandy walker the vermis is -

absent in 25% of cases

dandy walker malformation cause enlarged -

4th ventricle

enlarged posterior fossa

Holoprosencephaly -

• common large central ventricle

• single cerebrum

• absence of corpus callosum

• thin membrane from roof of 3rd ventricle

• possible formation of a supratentorial cyst

Holoprosencephaly -

failure of cleavage of the prosencephaly

3 types of holoprosencephaly -

• Alobar

• Semi lobar

• Lobar

Alobar -

• MOST SEVERE

• single ML ventricle

• no falx

• no CC

• fused thalami

• no third ventricle

semilobar -

• single ventricle

• some brain parenchyma

• portions of falx

• splenium of CC

partial 3rd ventricle

lobar -

• near complete separation

• falx present

• no CSP

• fused anterior horns of lateral ventricles

Congenital hydrocephalus -

imbalance between production and absorption/drainage of CSF

earlier onset of hydrocephalus =

greater enlargement of the head

hydrocephalus appearance -

• widely separated sutures

• huge buldgng fontanelles

most common cause of hydrocephalus is -

aqueduct stenosis

Communicant hydrocephalus -

• CSF pathways are open

• Impeded by occlusion of the subarachnoid cisterns

In communicant hydrocephalus there is decrease in -

absorption of CSF

Communicant hydrocephalus causes the -

entire ventricular system to become uniformly distended

Obstructive Hydrocephalus -

• interference in the CSF within the ventricular system

• Enlargement of ventricle cavities PROXIMAL to the obstruction

Subarachnoid cysts are lined by -

arachnoid tissue and contain CSF

Subarachnoid cysts may be -

supra or infratentorial

infratentorial Subarachnoid cysts in the posterior fossa -

• normal vermis

• normal 4th ventricle

subarachnoid cysts are a differential of

dandy walker malformation

Mostr frequent locations of subarachnoid cysts -

• interhemispheric fissure

• suprasellar region

• cerebral convexities