What is the Difference Between Cystic Hygroma and Nuchal Translucency?

Cystic hygroma and nuchal translucency are both fluid-filled spaces seen on fetal ultrasound, but they have distinct differences:

• Cystic Hygroma:
• A large single or multilocular fluid-filled cavity located in the nuchal region, behind and around the fetal neck, which can extend the length of the fetus.
• Can be seen as early as an 11-week ultrasound.
• Aneuploidy (chromosomal abnormalities) is present in 50% of cases.
• Most commonly associated with Trisomy 21 (Down Syndrome), 45X, and Trisomy 18.
• <20% of cases result in a healthy live-born infant at term.
• Nuchal Translucency (NT):
• A fluid-filled space normally seen behind the fetal neck on ultrasound performed in the first trimester.
• A key component of fetal aneuploidy screening, where size measurement is used as a risk factor for genetic disorders.
• Enlarged nuchal translucency is associated with cystic hygroma or mesenchymal edema.
• Outcomes in nuchal translucency less than 3.5mm are compared with NT of 3.5mm or greater in first-trimester fetuses with cystic hygroma.

In summary, cystic hygroma is a large fluid-filled cavity that can extend the length of the fetus and is associated with chromosomal abnormalities, while nuchal translucency is a normal fluid-filled space seen behind the fetal neck on ultrasound, and its size measurement is used as a risk factor for genetic disorders.

Comparative Table: Cystic Hygroma vs Nuchal Translucency

Here is a table comparing the differences between cystic hygroma and nuchal translucency:

Cystic hygroma is a type of birth defect that appears as an abnormal growth on an infant, while nuchal translucency is a normal fluid-filled space seen behind the fetal neck on ultrasound. Although both structures appear in the fetal neck, cystic hygroma is an abnormal structure, whereas nuchal translucency is a normal structure.