Ultrasound Imaging of Cervical Anatomic Variants

Abstract

Embryologic developmental variants of the thyroid and parathyroid glands may cause cervical anomalies that are detectable in ultrasound examinations of the neck. For some of these developmental variants, molecular genetic factors have been identified. Ultrasound, as the first-line imaging procedure, has proven useful in detecting clinically relevant anatomic variants. The aim of this article was to systematically summarize the ultrasound characteristics of developmental variants of the thyroid and parathyroid glands as well as ectopic thymus and neck cysts. Quantitative measures were developed based on our findings and the respective literature. Developmental anomalies frequently manifest as cysts that can be detected by cervical ultrasound examinations. Median neck cysts are the most common congenital cervical cystic lesions, with a reported prevalence of 7% in the general population. Besides cystic malformations, developmental anomalies may appear as ectopic or dystopic tissue. Ectopic thyroid tissue is observed in the midline of the neck in most patients and has a prevalence of 1/100,000 to 1/300,000. Lingual thyroid accounts for 90% of cases of ectopic thyroid tissue. Zuckerkandl tubercles (ZTs) have been detected in 55% of all thyroid lobes. Prominent ZTs are frequently observed in thyroid lobes affected by autoimmune thyroiditis compared with normal lobes or nodular lobes (P = 0.006). The correct interpretation of the ultrasound characteristics of these variants is essential to establish the clinical diagnosis. In the preoperative assessment, the identification of these cervical anomalies via ultrasound examination is indispensable.

Keywords: Cervical anomalies; cervical cysts; cervical ultrasound; parathyroid gland anomalies; thyroid anomalies; zuckerkandl tubercles (ZTs)..

Fig. (1)

Hypoplastic thyroid lobe in a male patient aged 47 years. a): Normal-sized right lobe (volume approximately 6.8 mL). b): Hypoplastic left lobe (volume approx. 0.3 mL). Both lobes are shown in transverse and longitudinal directions. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (2)

Lingual thyroid in a 15 year old female patient. a) The ultrasound examination in transverse direction demonstrates a sublingual mass with an echogenicity equal to thyroid tissue. b) The thyroid scintigraphy using 99mTechnetium-pertechnetate reveals a tracer uptake in the sublingual region and thus confirms the lingual thyroid.

Fig. (3)

Grading of Zuckerkandl Tubercles. Grade 0 represents an unrecognizable tubercle, grade 1 represents only a thickening of the lateral edge of the thyroid lobe, grade 2 represents tubercle smaller than 1 cm, and grade 3 represents larger than 1 cm in normal thyroid glands (blue columns), autoimmunethyroiditis (AIT) (red columns) and nodular goiters (green columns). (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (4)

Ectopic thymus tissue adjacent to the left thyroid lobe in a 33 year old female patient. The ultrasound image in transverse and longitudinal directions shows slightly isoechogenic tissue with punctuate hyperdense lesions (histologically confirmed). (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (5)

Median neck cyst in a 32 year old female patient. The median neck cyst is depicted in the longitudinal and transverse direction. The cyst has a volume of 2mL and lies in the ventral and lateral position of the trachea. (A higher resolution / colour version of this figure is available in the electronic copy of the article).