Nuchal Translucency and Cystic Hygroma

 

NT 

Tip 1:-Routinely  apply both Abd route of Usg TAS (95% access) & as well as TVS. If in a woman both  routes are employed then near 100% chance of perfect estimation . The calipers must be extra sensitive to record up to  0.1 mm accuracy in the machine.

NT alone can pick up Downs detection rate of 77% with false + of 5%. But addition of serum markers  patients age and associated foetal  cardio vascular abnormalities will increase the chance of detection of abnormal karyotypic disorders .  Gestational age dependent variation in either express as mm or as MOM .Quite often during  NT scan cystic hygroma may be visible - in that situation one should - then proceed for CVS,

 

 

NT when ?

CRL = 38 -84 mm; or gest ages 10 weeks 3+ to 13 +6 days . The lymphatic accumulation is  due to CCF  / abnormal  matrix of neck / abnormal  Ly drainage

Normal value :-

95% cetile is 0.8 mm above the normal median.

The difference between NT measurements and appropriate normal median for gest.

 

What other diagnois may be made during N T scan ?  Other CM likes   ? Abd wall hernia, skeletal dysplasia,  cardiac abnormalities  ( More high NT more is prevalent congenital heart disease  

Nuchal Translucency is not to be confused with nuchal Fold.

The association between nuchal edema and aneuploidies has been described for the first time in 1987 by Benacerraf after having observed a thicker subcutaneous nuchal fold between 16 and 18 weeks of gestation in fetuses referred for amniocentesis because of advanced maternal age. The same data have been described four years later by Nicolaides et al observed earlier in pregnancy at 11-14 weeks.

 

Dilemma 1 : When to measure NT??  The observation of a nuchal liquid fold behind the fetal neck , measurable at 11-14 weeks and the association between increased NT and chromosomal abnormalities ( or other fetal conditions ) represents the basis on which the first trimester screening has been developed .

Dilemma 2: Why fluid accumulates?  The pathophysiology of the increased NT is multifactorial. Possible cases are extracellular matrix anomalies cardiocirculatory and lymphatic abnormalities.

Dilemma 3  :How to pickup cystic hygroma??  Some authors use to describe as cystic hygroma the cases of markedly increased NT with septations within the translucency and they use to consider this finding  as more severe than a simply increased NT and different from it .

 

Dilemma 5: Management of cystic hygroma and raised NT have almost similar onward investigative protocol & management : Actually these two pathologies have the same pathogenic mechanisms and similar pathologic correlations. The double nomenclature of the same pathology could cause misunderstandings as the two findings have the same management, and the seriousness of an increased NT just depends on how thicker than normal it is.