Fetal Brian Development

Part 1指導

洪正修主任 楊明智主任

陳志堯2006.12.15

Anatomy

Head and neck

• Cerebellum• Choroid plexus• Cisterna magna• Lateral cerebral ventricles (Atrium)• Midline falx• Cavum septi pellucidi

AIUM guideline

Embryologic Events

• 3rd~4th wk neural plate and folds appear– 3 major divisions of brain – Prosencephalon (forebrain)– Mesencephalon (midbrain)– Rhombencephalon (hindbrain)

• 5th week further division of 3 primary

brain vesicles

• After 5th Further differentiation

Five Cephalons 9+ wks

Prosencephalon

Rhombencephalon

Neural tube & folds

3~4th wk

Prosencephalon (forebrain)

Mesencephalon (midbrain)

Rhombencephalon (hindbrain)

Telencephalon

Diencephalon

Metencephalon

Myelencephalon

5th wk

1. Cerebral hemisphere

2. Choroid plexus

3. Internal capsule

4. Olfactory bulbs and tracts

1. Thalamus2. Optic nerve

3. Geniculate & mamillary body4. Pineal and pituitary glands

Pons, cerebellum

Medulla

Exencephaly, Anencephaly• Absence of cranial vault and varying amount of su

pratentorial brain.

• Neural tissue wears away.

• Neural tissue make D/D between Ex and An.

• Mickey Mouse sign or Bart Simpsom appearance.

• CRL less than expected.

Exencephaly, Anencephaly 續 1

• 2nd and 3rd trimester: neural tissue dissolved.• Protuberant eyes.• Multi-factorial.• Risk Factor~

– Folic acid deficiency– Insulin-dependent diabetes– Hyperthermia– MTX, valporic acid, carbamazepine…(FA antagoni

st)

Exencephaly, Anencephaly 續 2

• Epidemiology~ 1:1000 (UK)• M:F 1:4• Associated anomalies:

– Spinal bifida 27%– GU: 16%– Cleft lip/palate: 10%– GI: 6%– Cardiac: 4%

Video Time

Agenesis of Corpus Callosum• ACC/Callosal dysgenesis

• Ultrasound Findings~– Mild ventriculomegaly– Colpocephaly (teardrop-shaped ventricle)– Prominent of interhemispheric fissure (IH cyst)– Elevation of 3rd ventricle– Absent of cavum septi pellucidi– Abnormal course of pericallosal artery– Other CNS anomalies: 50%– Lipomas (hyperechoic midline mass; 50% have ACC)

Agenesis of Corpus Callosum 續 1• Chromosomal anomalies in 10~20%: Trisomy 1

8,13, 8• Teratogens: alcohol, cocaine, valproate• Infection: CMV & rubella• 0.3~0.7% of general population, M>F• Fetal body anomalies seen in 60%

Thanks for Attention!

My son, give attention to my words; let your ear be turned to my sayings.

Let them not go from your eyes; keep them deep in your heart.

For they are life to him who gets them, and strength to all his flesh.

And keep watch over your heart with all care; so you will have life.

Proverb 4:20~23

QUIZ TIME

1. 小腦到幾週發育完成 ?2. True BPD view 可以看到哪最重要之三

個腦部結構 ?3. Absence of corpus callosum 在超音波

底下典型的 signs ，試列出兩項。