1. Radiology department, Kasr Alainy hospitals, Cairo University, Egypt;
2. Fetal medicine unit, Cairo University, Egypt.

Case report:

A 30-year old woman (G2P1) presented to us at 25 weeks gestation to exclude fetal goiter as a result of maternal medical history of Grave's disease that was active until 14 weeks of gestation at which the mother started propylthiouracil therapy and she was euthyroid at time of scan. Ultrasound examination revealed:

- Diffuse homogeneous enlargement of the thyroid gland presented as a solid lower anterior neck mass surrounding the trachea with color Doppler study showing marked increase in thyroid gland vascularity (thyroid inferno pattern) predominantly central vascularization with mild peripheral Doppler flash. Mild tracheal compression is noted with no evidence of polyhydramnios.
- Fetal heart rate was on the upper limit of normal values (155-160 bpm) for this gestational age (25 weeks) and we could define it as a borderline tachycardia.
- Cardiac assessment revealed dilated innominate veins and right SVC (larger that ascending aorta and main pulmonary artery) with moderate tricuspid regurgitation. Yet, there was no evidence of ventricular disproportion or right heart dominance.
- Normal fetal growth (GA 25 weeks and 3 days by combined fetal biometry with estimated fetal weight 780 gm). No signs of fetal growth restriction with oligohydramnios, significant tracheal compression with polyhydramnios or fetal hydrops. The rate of fetal bone maturation could not be assessed at this gestational age.
- Fetal movements were increased at time of scan (over a period of 40 minutes scanning).

Images 1-4; videos 1-4: Axial and coronal views in 2D and color Doppler exam showing the fetal goiter with mild tracheal compression and dominant central vascularization.

Images 5-8; videos 5-9: show the dilated inominate veins and SVC with moderate TR, no ventricular disproportion or right heart dominance.

Image 9: FHR on the upper limit of normal (155-160 bpm).

Based upon maternal history of active autoimmune thyroid disease and the delayed start of antithyroid therapy till 14 weeks of gestation due to poor antenatal care, fetal hyperthyroid goiter was expected. Ultrasound features were in agreement with this clinical expectation (fetal goiter with dominant central vascularization, borderline tachycardia and the dilated SVC and innominate veins with moderate tricuspid regurgitation due to intra glandular significant arterio venous shunting mimicking the hemodynamic effect of arterio venous malformation like vein of Galen aneurismal malformation. Fetal cord blood sampling was not done.

The mother was euthyroid at presentation due to start of anti thyroid therapy at 14 weeks gestation.  Medical treatment and close follow up of fetal well-being, size of goiter, the rate of bone maturation at 31 and 35 weeks gestation with serial fetal heart rate monitoring were done and revealed stabilization of fetal condition (regression of fetal heart rate to normal values with reduction is size of thyroid gland and no signs of growth restriction, tracheal compression or heart failure) with normal rate of bone maturation. A male baby was born through a cesarean section with mild goiterous features and mild elevation of thyroid hormones. The neonatal condition was stabilized on medical treatment at the first month of life with uneventful postnatal course. 

At 2009, Huel and his colleagues described an ultrasound score for evaluation of fetal goiter to illustrate whether it appears as a result of hypo or hyperthyroidism¹. In our case, the prevalence of central vascularization (thyroid inferno pattern) with borderline tachycardia takes the score of 2 in agreement with hyperthyroidism. However, the appearance of dilated innominate veins and SVC as a consequence of significant intra glandular arterio venous shunting could be another sonographic clue for the diagnosis of fetal hyperthyroid goitre as it occurs very frequent with thyrotoxicosis.

References:

1-Huel, C., Guibourdenche, J., Vuillard, E., Ouahba, J., Piketty, M., Oury, J.F. and Luton, D. (2009). Use of ultrasound to distinguish between fetal hyperthyroidism and hypothyroidism on discovery of a goiter. Ultrasound in Obstetrics & Gynecology, 33(4), pp.412-420.