Neck Flashcards
What are the fetal anomalies associated with the Neck?
3
Cervical Teratoma
Cystic Hygroma
Thyroid Goitre
Cervical Teratoma
Prevalence: 1 in 50,000 births.
5% of all fetal teratomas.
Ultrasound: Vascular solid mass with cystic components, located anterior or anterolateral to the fetal neck. The tumor grows rapidly (especially >26 weeks’ gestation due to materal estrogens) and can extend inwards producing hyperextension of the neck and polyhydramnios.
Calcifications are found in about 50% of cases.
Assoc abnorm: The incidence of chromosomal defects and genetic syndromes is not increased.
Large tumours may result in fetal anemia and thrombocytopenia (due to sequestration of red blood cells and platelets by the tumor), fetal heart failure, hydrops and placentomegaly (due to a hyperdynamic circulation as a result of arteriovenous shunting), polyhydramnios (due to direct transudation into the amniotic fluid and due to fetal polyuria, secondary to the hyperdynamic circulation) and maternal mirror syndrome (generalized fluid overload and preeclampsia).
Follow up: Follow-up scans every 2 to 3 weeks to monitor growth of the tumor, heart function, MCA PSV and amniotic fluid volume.
Prognosis: Fetal or neonatal death (due to airway obstruction) in about 80% of cases.
Survival after surgery is >80% however, extensive neck dissection and multiple additional procedures are necessary to achieve complete resection of the tumor with acceptable functional and cosmetic results.
Recurrence: No increased risk of recurrence.
Cystic Hygroma
Prevalence: 1 in 800 pregnancies.
1 in 8,000 live births.
Ultrasound: Bilateral symmetrical cystic structures located in the occipital-cervical region of the fetal neck. They are differentiated from nuchal edema by the presence of the nuchal ligament (midline septum).
Cystic hygroma is caused by defects in the formation of the neck lymphatics. It is the most common form of lymphangioma (75% are located on the neck, 20% in the axillary region and 5% on the chest wall, abdominal wall and extremities).
Assoc abnorm: Chromosomal abnormalities, mainly Turner syndrome, are found in about 50% of cases.
Genetic syndromes are found in about 40% of cases. The most common are Noonan syndrome (autosomal dominant but >90% are due to de novo mutations; cystic hygromas, hypertelorism, pulmonary stenosis, fetal growth restriction), Multiple-pterygium syndrome (autosomal recessive; cystic hygromas, contractures in all joints, microcephaly and micrognathia), Fryns syndrome (autosomal recessive; anophthalmia, facial cleft, micrognathia, ventriculomegaly, diaphragmatic hernia) and Neu-Laxova syndrome (autosomal recessive; hypertelorism, microcephaly, agenesis of corpus calosum, contractures in the upper and lower limbs, fetal growth restriction).
Hydrops (in addition to cystic hygromas there is generalized edema, ascites, pericardial or pleural effusions) occurs in 60-80% of cases.
Follow up: Follow-up scans every 4 weeks to assess the evolution of the hygromas and development of hydrops.
Prognosis: Fetal death: 90%.
In 10% of cases the fetal karyotype is normal, there are no other obvious defects and the hygromas resolve during pregnancy. In these cases the prognosis is good.
Recurrence: Isolated or part of Turner syndrome: no increased risk of recurrence.
Part of autosomal recessive syndroms: 25%.
Thyroid Goitre
Prevalence: 1 in 5,000 births.
Ultrasound: Anterior cervical echogenic mass of variable size. The fetal head may be hyperextended and polyhydramnios is common due to mechanical obstruction of the esophagus.
Most cases of fetal thyroid goitre are the consequence of fetal hypothyroidism due to transplacentally derived anti-thyroid drugs used for the treatment of maternal hyperthyroidism. A less common cause of hypothyroid goitre is congenital dyshormonogenesis due to defects in genes involved in the pathway of thyroid hormone production. In hypothyroidism the fetus may have impaired growth and bradycardia.
Hyperthyroid goitre is rare and it is caused by transplacentally derived maternal thyroid stimulating immunoglobulins in recently diagnosed Graves’ disease. The fetus may have impaired growth, tachycardia, heart failure and decreased movements.
Assoc abnorm: The incidence of chromosomal abnormalities and genetic syndromes is not increased.
Follow up: Every 4 weeks to monitor fetal growth, size of the tumor, fetal heart rate, amniotic fluid volume and cervical length.
Prognosis: Good.
Untreated congenital hypothyroidism is associated with neurodevelopmental delay.
Recurrence: Thyroid dyshormonogenesis is autosomal recessive: 25%.
The rest of cases: no increased risk of recurrence.
