Ultrasonographic assessment of the ectopic thyroid tissue in children with congenital hypothyroidism.

BACKGROUND

Ectopic thyroid tissue as a result of thyroid developmental abnormalities is the most frequent cause of congenital hypothyroidism (CH). It is diagnosed by using radionuclide thyroid scanning. OBJECTIVE. To evaluate the sensitivity of US in the detection of such ectopias and to describe their US pattern before and during treatment.

MATERIALS AND METHODS

Forty-two neonates (group A; aged 11.3+/-4.0 days) and 33 older children (group B; aged 11.1+/-3.9 years) with a biochemical diagnosis of CH and thyroid ectopia detected by radionuclide scanning were evaluated before (group A) and after (group B) treatment. Thyroid US included a survey of the pathway of the thyroglossal tract and an evaluation of the location, size, echogenicity and vascularity of any tissue along this pathway suggestive of thyroid ectopia.

RESULTS

Thyroid ectopia was detected using US in 18 patients (24%) with a similar rate during the neonatal period and thereafter on therapy. Three patients demonstrated double ectopia. These 21 sites of ectopic thyroid tissue were located at the suprahyoid level (n=12), at the level of the hyoid (n=1), and at the infrahyoid level (n=8). The maximum diameter of the ectopic tissue ranged from 4 to 14 mm. In group A (9 patients), the 11 ectopias were all hypervascular. These were hyperechoic in all but one neonate. In group B (9 patients), the ten ectopias were not vascular, and were hyper (n=3) or hypoechoic (n=7).

CONCLUSIONS

US allows for detection of ectopic thyroid tissue, but with a lower detection rate than radionuclide scanning. However, it does provide a more detailed description of such ectopias.