Fetal Head

list the intracranial parts

• cerebrum

• falx cerebri

• lateral ventricle

• choroid plexus

• thalamus

• cerebral peduncles

• 3rd ventricle

• cave septum pellucidum

• cerebellum

• cisterna magna

list the extracranial parts

• nuchal fold

• profile

• nasal bones

• lips/nares

• orbits

Cerebrum

large hemispheres of brain tissue

what is the cerebrum separated by?

the falx cerebri

cerebrum on US

is hypoechoic

when can you see the sulci?

late in pregnancy

what view?

long

what view?

coronal

what view

axial

falx cerebri

• fold of dura matter that divides the cerebral hemispheres

• hyperechoic line

lateral ventricle (LV)

• two largest cavities of the ventricular system

  • contain CSF made by the choroid plexus

what are the sections of the lateral ventricle?

• frontal horn

• body

• atrium

• occipital horn

• temporal horn

the frontal horn is…to the thalami

anterior

the frontal horn is…to the CSP

lateral

the frontal horn is prominent with?

ventricular dilation

the lateral ventricle is… and…to the thalami

superior and lateral

the lateral ventricle is usually…during the 2nd/3rd trimester?

collapsed

the lateral ventricle is not well visualized with US unless…

dilated

occipital horn is…and…to the thalami

posterior and inferior

temporal horn is not well visualized in US unless?

dilated

atrium

• junction of the LV body, occipital, and temporal horns

• located inferior to the mid skull

• posterior/lateral to the thalamus and 3rd ventricle

• usually filled with hyperechoic choroid plexus

• measurement:

  • across posterior portion

  • posterior LV

  • less than 10mm is normal

Choroid plexus

• located within the ventricles

• produces CSF

• appears hyperechoic

Thalamus

• located centrally in the brain

  • inferior to the falx

  • superior to midbrain

• consists of two lobes

  • encase the 3rd ventricle

• diamond or heart shaped

• hypoechoic relative to the cerebrum

cerebral peduncles

• 2 symmetric anterior protrusions of the midbrain

• located centrally in the brain and lie slightly inferior to the 3rd ventricle and thalamus

• lie posterior to the circle of willis

• appears hypoechoic and smaller than the thalamus

3rd ventricle

• located centrally in the brain

• inferior to the lateral ventricles

• typically collapsed and only enlarged with pathology

cave septum pellucidum (CSP)

• fluid filled, midline structure

• located between the anterior flax and 3rd ventricle

• two echogenic lines lateral to the falx

cerebellum

• divided into two hemisphere that are connected by the vermis

• hypoechoic and barbell butterfly shaped

• measurement should correspond to GA after 16w

• evaluate shape (banana shape associated with Arnold chair II malformation)

Cisterna Magna

• fluid filled cavity in the posterior skull

• posterior to the cerebellum and anterior to the occipital bone

• normal 3-10mm

• measure after 16w

nuchal fold

• skin that covers the inferior mid occipital bone and posterior neck

• normal measurement is 18w-20w: <6mm

• measure outside occipital bone outer skin edge

evaluate profile for?

abnormal contour

• note shape of lips, nose, forehead, mandible

Nasal bone

• assess for presence or shortening of the nasal bone

• normal length > 2.5mm

Evaluating Lips

• check for cleft lip or palate abnormalities

• coronally

evaluate orbits

assess size of orbits and distance between orbits

orbital diameter (OD)

• measure a single fetal orbit

• measure inner diameter

Interocular distance (IOD)

measure the distance between the two orbits