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Routine fetal anatomy scan at 18-23 weeks
- 1. Ali Bendary Assistant Lecturer sonographicFetal anatomy at 18-23 weeks
- 2. history • Echolocation inbats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound and not vision. • The first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917. (The term SONAR refers to Sound Navigation and Ranging)
- 3. FaQ Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
- 4. what is thebest time For anatomical scanning ? • A routine mid-trimester ultrasound scan is often performed between 18 and 22 weeks of gestation. • Countries where pregnancy termination is restricted should balance detection rates against the time needed for counseling and additional investigation. • Some centers perform the anatomical survey using transvaginal scanning at approximately 13–16 weeks’ gestation. ISUOG GUIDELINES 2013
- 5. Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
- 6. what is thethe aim oF the routine mid-trimester scan ? 1- Confirm number and viability of fetuses 2- Determine site of the Placenta, assessment of amniotic fluid and umbilical cord. 3- Fetal biometry 4- Fetal anatomy 5- Fetal growth pattern - estimation of GA and EFW - assessment of fetal growth (single - multiple) 6- Fetal wellbeing (BPP – Doppler) 7- Select patients requiring referral to a tertiary center. ISUOG GUIDELINES 2013
- 7. who should havea mid-trimester Fetal ultrasound scan? • all pregnant women should be offered an ultrasound scan for the detection of fetal anomalies and pregnancy complications. ISUOG GUIDELINES 2013
- 8. First overview oFthe Fetus Psycological assurance of the mother. Broad view of the fetus: - Pulsating heart - Profile of the face - Both upper and lower limbs
- 9. Standard viewsfor theexamination ofthefetus 1) The skull and brain 2) The face 3) The chest: heart and lungs 4) The abdomen: Diaphragm, stomach, liver, kidneys, umbilical insertion 5) The spine 6) The limbs
- 10. Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
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- 12. Examination of thefetalbrain is essentially carried out by thethree Transverseplanes: • Transthalamic • Transventricular • Transcerebellar NEUROSONOGRAM?
- 13. Trans-ventricular plane Used formeasurement of Va and Vp
- 14. • V/H ratio? < 0.6 before 18 wks < 0.5 after 18 wks • Used for measurement of BPD and HC • Cephalic index: BPD/OFD = 80 ± 5 < 75 in doliocephaly > 85 in brachycephaly Trans-thalamic plane
- 15. Trans-cerebellar Plane - Calledsuboccipito-bregmatic view - Allows examination of posterior fossa and mid-brain - Used for measurement of TCD ( 13-21 wk? ), CM ( 2-10 mm ) and NF ( 6 mm )
- 17. NEUROSONOGRAM Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
- 18. Spine 3 views: nospinal defects or masses -Sagittal -Transverse -Coronal N.B. in sagittal view take care to reduce the pressure on the transducer to leave some amniotic fluid between the proximal uterine wall and the spine, which greatly enhances the acoustic window
- 19. Cerebralventriculomegaly - Grades: borederline(10-15mm) – moderate (15-20mm) – sever (>20mm) - Mild borderline (10-12mm) ?!! - Unilateral in destruction and bilateral in cases of malformation - Hydocephalus ?!!
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- 21. Ventriculomegaly: diagnostic work-up • Detailedultrasound exam including fetal echo • Fetal neuro-sonography in 2nd T or MRI in 3rd T • Karyotype (risk of triomy 21) • TORCH screen
- 22. Holoprosencephaly defect inthe development of the midline embryonic forebrain. Types : - Alobar - Semilobar - Lobar
- 25. •Risk of chromosomalanomalies: This is high (especially trisomy 13): up to 40% if other malformations are associated. •Risk of non-chromosomal syndromes: This is relatively high: 15–20% of cases.
- 26. AGENESISOFTHECORPUS CALLOSUM It is themajor commissure between the two cerebral hemispheres
- 30. Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
- 31. Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
- 32. Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
- 33. Posteriorcranialfossamalformations Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
- 34. Open 4th ventricle before20 weeks Pan Arab Conf for UMK of GYn OBS ultrasound 2nd May 2006
- 35. DANDY–WALKER MALFORMATION (DWM) - Cysticdilatation of the 4th ventricle occupying the whole of the cisterna magna - Partial or complete agenesis of vermis - upward displacement of tentorium - Enlarged posterior cranial fossa
- 36. BLAKE’S POUCH CYST(BPC) - Caudal expansion of the 4th ventricle resulted in finger like expansion of the PMA that does not perforate. - Not communicate with subarachnoid space
- 37. MEGACISTERNA MAGNA (MCM) -Enlarged CM which freely communicate with 4th ventricle and subarachnoid space - Normal vermis - Normal 4th ventricle - Normal tentorium - Normal posterior cranial fossa
- 38. Hydancephaly • huge fluidcollection filling the whole cranial cavity, • no recognizable cerebral cortex. • The falx is usually present • the meninges, thalami, basal ganglia, brainstem, and cerebellum may be normal.
- 39. NEURAL TUBE DEFECTS 1- ACRANIA/EXENCEPHALY/ANENCEPH ALY 2-CEPHALOCELE 3- SPINA BIFIDA
- 40. ACRANIA/EXENCEPHALY/ANENCEPHAL Y • Acrania: Absenceof the cranial vault. • Exencephaly: cerebral hemispheres visible in the amniotic fluid ‘Micey mouse’ appearance • Anencephaly: no cerebral cortex remaining Frog appearance of the orbits in the 2nd trimester (brain destroyed)
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- 42. Pan Arab Conffor UMK of GYn OBS ultrasound 2nd May 2006
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- 45. CEPHALOCELE • Cystic structureprotruding through a calvarial bone defect. • The herniated anatomic structures can consist of meninges only (meningocele) or meninges plus cerebral tissue (encephalomeningocele) • Prognosis depends on: size, site, contents and associated lesions.
- 50. D.D. - Absence of calvarialbony defect - Bilateral cystic dilatation at the back of neck with thick fibrous band (nuchal ligament)
- 53. SPINA BIFIDA - Refersto defective fusion of posterior spinal bony elements. -Spina bifida aperta = open spinal dysraphism (OSD) -Spina bifida occulta = closed spinal dysraphism (CSD) -Meningocele: herniation of the meninges through defect and there is a skin covering with no neural tissue -Myelomeningocele: herniation of the meninges with involvement of neural tissue covered by thin membrane -Myelocele: failure of the neural groove to close with subsequent exposure of neural tissue (the placode is flush with the cutaneous surface)
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- 57. CHIARI II MALFORMATION •Small posterior fossa • Obliterated CM • Dysmorphic cerebellum ( banana shaped) • Ventriculomegaly • Lemon sign • Meningeo-myelocele
- 58. Direct signs •axial andmid-sagittal planes: interruption of the cutaneous contour at the level of the affected vertebrae •axial views: the affected vertebra has a ‘C’ or ‘U’ shape, which is due to absence of the dorsal arches •coronal views: the lateral processes appear widely separated (loss of normal divergent rail-track appearance)
- 61. TAKE HOME MASSAGE (EFFECTIVENESSOF ULTRASOUND EXAMINATION OF THE FETAL NEURAL AXIS) In a low risk pregnancy around mid-gestation, if: The trans-ventricular plane, the trans-thalamic and the trans-cerebellar plane are satisfactorily obtained. The head measurements (head circumference in particular) are within normal limits for gestational age. The atrial width is less than 10.0 mm. The cisterna magna width is between 2–10 mm. many cerebral malformations are excluded, the risk of a CNS anomaly is exceedingly low and further examinations are not indicated
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