FETAL HEAD

macrosomia

• birth weight of 4000g or greater

• above 90th percentile

commonly result of poorly controlled maternal diabetes

what distinguishes microcephaly from anencephaly

intact calvarium

key sono of microcephaly

• BPD or HC is 2-3 standard deviations below mean expected for GA

• abnormal fetal biometric ratio

brachycephaly

head is rounder than usual

dolichocephaly

narrow BPD and long occipitofrontal diameter (OFD)

lemon sign

fetal head with bilateral denting of frontal bones

• associated with spina bifida

cloverleaf skull

tri-lobed appearance of the head

• associated with thanatophoric dysplasia and homozygous achondroplasia

strawberry shaped skull

fetal head with normal BPD and narrow frontal diameter

• associated with trisomy 18

spalding sign

flattened and misshapen fetal head with overlapping of cranial bones

• associated with fetal demise

scalp edema

• fetal hydrops and scalp thickening (>/= 3mm)

presence of the _______ excludes agenesis or corpus callosum

CSP

what is agenesis of corpus callosum m/c associated with

dandy walker malformation

sono of ACC

• absence of CSP

• colpocephaly (disproportionate prominence of occipital horns of lateral ventricles) bullet shaped

• sunburst appearance

intracranial calcifications are most commonly the result of

fetal viral infection (cytomegalovirus m/c)

what is the most common intracranial tumour

teratoma

aqueductal stenosis

results from obstruction, atresia, stenosis of aqueduct of sylvius

• causes ventroculomegaly

sono of aqueductal stenosis

• ventriculomegaly

• 3rd ventricle dilaltion

• flexion and adduction of thumb

vein of galen aneurysm

fusiform median cyst in the region of the transverse fissure immediately superior to the cerebellum

• abnormal turbulent Doppler signals within the aneurysm

acrania

absence of normal cranial vault with a normal appearing or disorganized brain above orbits

increased maternal serum AFP is associated with

open neural tube defects

anencephaly

• absence of cranial vault, complete or partial absence of forebrain,

• presence of brainstem, midbrain, skull base, facial features

sono of anencephaly

• no normal cranial morphology and brain tissue above orbits

• exophthalmos (bulging of eyes)

cephalocele

neural tube defect in which meninges alone or meninges and brain herniate through defect in calvarium (no increase in AFP)

• meningocele: meninges only

• encephalocele: brain tissue only

• encephalomeningocele: brain tissue and meninges

encephalocele

ventriculomegaly

dilation of cerebral ventricles without defining the cause

m/c causes of ventriculomegaly

• arnold chiari (3rd, 4th, lateral ventricles dilated)

• open NTDs

• double aqueduct stenosis

• dandy walker

hydrocephaly

ventriculomegaly most commonly associated with increased intracranial pressure

• usually due to lesion causing obstruction

aqueduct of sylvius obstruction causes enlargement

of lateral ventricles and 3rd ventricle

what is holoprosencephaly

incomplete separation of the two hemispheres

what is holoprosencephaly m/c associated with

Trisomy 13

• also 18

alobar holoprosencephaly

• mono ventricle

• fused thalamus

• no fissure, CSP, CC

semilobar holoprosencephaly

• single ventricle cavity

• partial/complete fused thalami

• rudimentary flax

• no CSP, CC

lobar holoprosencephaly

• almost complete division of ventricles

• CC may be present

• CSP still absent

hydranencephaly

absence of cerebral hemispheres with an incomplete or absent falx and sac-like structure contain CSF surrounding brainstem and basal ganglia

sono of hydranencephaly

• brainstem, cerebellum, cisterna magna unaffected

• lacking a mantle or rim of cerebral brain tissue

schizencephaly

clefts in the cerebral mantle with communication between the ventricles and subarachnoid space

dandy-walker malformation

• agenesis or hypoplasia of cerebellar vermis

• dilated 4th ventricle

• enlarged posterior fossa (cisterna magna)

arachnoid cyst

benign cyst in the cerebrospinal axis

• do not communicate with ventricular system

porencephaly

cysts filled with cerebrospinal fluid that communicate with ventricular system or subarachnoid space

arnold chiari type II

• displacement of cerebellar tonsils, part of cerebellum, 4th ventricle, pons and medulla oblongata

• accompanied by hydrocephalus and myelomeningocele

what is the main sono finding in chiari type 2

banana sign

• (curved cerebellum)