Fetal Brian Development Part 1 指導 洪正修主任 楊明智主任 陳志堯

Anatomy

Head and neck Cerebellum Choroid plexus Cisterna magna Lateral cerebral ventricles (Atrium) Midline falx Cavum septi pellucidi AIUM guideline

Embryologic Events 3 rd ~4 th wk neural plate and folds appear –3 major divisions of brain –Prosencephalon (forebrain) –Mesencephalon (midbrain) –Rhombencephalon (hindbrain) 5 th week further division of 3 primary brain vesicles After 5 th Further differentiation

Five Cephalons 9 + wks Prosencephalon Rhombencephalon

Neural tube & folds 3~4th wk Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephal on (hindbrain) Telencephalon Diencephalon Metencephalon Myelencephalon 5 th wk 1.Cerebral hemisphere 2.Choroid plexus 3.Internal capsule 4.Olfactory bulbs and tracts 1.Thalamus 2.Optic nerve 3.Geniculate & mamillary body 4.Pineal and pituitary glands Pons, cerebellum Medulla

Exencephaly, Anencephaly Absence of cranial vault and varying amount of supratentorial 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 antagonist)

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 18,13, 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。