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Nuchal translucency

Nuchal translucency
It is a sonographic pre natal screening scan to detect cardiovascular abnormality in a fetus.
NT can also detect altered extra cellular matrix composition and limited lymphatic drainage

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Nuchal translucency

  1. 1. Nuchal Translucency Guided by: Dr. Sangeeta Saxena Professor and Head Department of Radiodiagnosis Presented by : Dr. Vrishit Saraswat I Year Resident M.D. Radiodiagnosis
  2. 2. Nuchal Translucency • It is a sonographic pre natal screening scan to detect cardiovascular abnormality in a fetus. • NT can also detect altered extra cellular matrix composition and limited lymphatic drainage
  3. 3. Q. How NT develops • The actual anatomoical structure which is seen as “Translucency “ is most likely the normal skin at the back of neck.
  4. 4. Physiology behind NT Placental Circulation Fetal Circulation Between 11-14 wks of gestation Increased Resistance Under develop Lymphatic Channels Later in gestation Decreased Resistance Improved Lymphatics which are able to drain away excess fluid
  5. 5. • BUT whenever there is alteration in normal embryological condition , NT may become oedematous or in some cases , filled with fluid by dilated lymphatic channels. • Example in down syndrome due to cardio vascular abnormality such as ASD or VSD , the CVS and lymphatics are incompatible to drain the excess fluid causing NT to increase.
  6. 6. Other Chromosal abnormalities associated with increase NT • Turner Syndrome (45 X) • Edward Syndrome (tri 18) • Patau Syndrome (tri 13) • Di-george Syndrome (del 11q22)
  7. 7. Non chromosomal abnormalities associated with increased NT • Altered extra cellular matrix composition, i.e. defect in Proteoglycans & GAGs. • Limited / underdeveloped lymphatic drainage also cause NT to increase
  8. 8. OTHER CONDITIONS ASSOCIATED Several other structural abnormalities might be seen at nuchal translucency screening like : 1. Omphelocoele 2. Anencephaly 3. Micrognathia 4. Megacystis
  9. 9. FIRST TRIMESTER SCREENING FOR ANEUPLOIDY • Nuchal Translucency : >95 percentile for CRL OR >2.5mm is consider as increased NT, According to several studies , the sensitivity of NT alone, for detection of Tri-21 is around 60 – 70%.
  10. 10. • Serological Marker : Triple Test It is done by evaluating the levels of A Alpha fetoprotein B Beta HCG C Triol i.e estratriol with low level of PAPP-A Serological marker alone have sensitivity of 65% to detect Tri-21 Continue…..
  11. 11. • Combined Screening : First Trim.Screening using NT and Serological markers(increased b-HCG and decreased PAPP-A)have been used in various studies and it is found out to be more sensitive than either of them individually The detection rate of Tri-21 was 87 , 85 and 82 % in 11, 12 and 13 wks. Gestation respectively. Continue….
  12. 12. • Exception to this is multiple pregnancy where detection rate was 88% with NT alone.
  13. 13. Q. Can NT alone be considerable enough? • According to several studies conducted : • If NT more >3 mm , there is “minimal” benefit in waiting for combined screening. • If NT is >4mm , there is “NO” benefit in waiting for combined screening.
  14. 14. Integrated and Sequential Screening • Involves two steps: Step 1: In first trimester NT + PAPP-A Step 2: In second trimester Quadriple Test ( Triple test+ Inhibin)
  15. 15. Nasal Bone assesment
  16. 16. Cystic Hygroma
  17. 17. Standardization of Nuchal Translucency measurement technique 1. Callipers must be able to be adjusted in increments of 0.1 mm 2. Approximately 20 mins. should be given to obtain required measurements 3. CRL must be between 38-84 mm 4. Clear NT margins 5. Fetus horizontal image 6. Fetus in mid sagittal plane
  18. 18. 7. Tip of nose in profile 8. Head , neck and upper thorax should fill the image with no visualization of heart. 9. Head in Neutral Position 10. Pocket of fluid should be visible between chin and neck 11. Angle of neck and chest should be <90 deg.
  19. 19. 12.Callipers are placed at inner border of lucent line 13. Lucency measured perpendicularly and in widest space 14. Measure NT three times and report the largest of three technically correct measurements.
  20. 20. Any Suggestion or Additional Information is Welcomed Thanks & Regards Dr. Vrishit Saraswat