Ultrasound anatomy of the tongue in human fetuses during prenatal screening

Background.The tongue is in close topographic and anatomical relationship with the organs of the maxillofacial region, and its anomalies are often associated with syndromic pathology. Standard prenatal ultrasound screening protocols do not include mandatory assessment of this organ.

The aim of this studywas to obtain new quantitative parameters of the tongue in human fetuses during prenatal ultrasound screening.

Materials and methods.An analysis of 120 ultrasound scans of human fetuses aged 11–14 (n=30), 19–21 (n=60), and 30–34 (n=30) weeks was conducted. The methods included ultrasound scanning, morphometry, and statistical analysis. Linear dimensions of the tongue, perimeter, surface area, topographic distances to surrounding structures, as well as parameters of the lingual and deep lingual arteries were assessed.

Results.Ultrasound scanning at 11–14 weeks revealed that the tongue has a rounded flattened shape with heterogeneous echostructure and unclear borders. By 19–21 weeks, it acquires an oval shape, occupies 86±5,6% of the oral cavity cross-sectional area, its grooves become visible, and motor activity is registered. At 30–34 weeks, the lingual frenulum is clearly visualized for the first time, and contractions of individual muscle elements are recorded. Mean values were obtained for longitudinal (from 10,0±1,2 to 27,5±2,0 mm), transverse (from 6,5±0,7 to 22,1±2,1 mm), and vertical (from 2,4±0,9 to 7,5±0,9 mm) dimensions of the tongue, perimeter (from 25,0±1,2 to 87,1±7,0 mm), surface area (from 41,2±8,2 to 487,3±22,9 mm2), as well as diameter of the lingual (from 0,7±0,2 to 2,1±0,3 mm) and deep lingual (from 1,4±0,2 to 1,2±0,3 mm) arteries. Topographic distances from the tongue to the hard palate, mandible, oral diaphragm, and posterior pharyngeal wall were established for 19-21 and 30–34 weeks. Uneven growth was revealed: from the first to the second screening, the maximum growth rate was demonstrated by the surface area of the tongue (125%) due to an increase in the transverse size (77%), which was accompanied by an active increase in the diameter of the lingual artery (91%); from the second to the third trimester, longitudinal elongation of the tongue predominated (50%) with stabilization of the parameters of its arteries (15–16%). The angle between the root, dorsum, and apex of the tongue consistently decreases from 158±11° to 115±6°. The identified mean values for the linear dimensions of the tongue are consistent with published data. However, the vertical dimension, surface area, parameters of arteries, and topography of the tongue have not been previously described. The established heterochronic growth reflects the patterns of maxillofacial morphogenesis.

Conclusions. Ultrasound visualization of the tongue in human fetuses is feasible during prenatal screenings at 11–14, 19–21, and 30–34 weeks. The average values for the longitudinal, transverse, and vertical dimensions, perimeter, and surface area of the tongue increase unevenly over the studied period. An assessment of tongue topography at 19–21 and 30–34 weeks of development allowed us to quantify its position and reveal that the angle between the root, dorsum, and apex of the tongue decreases, resulting in an arched position in the oral cavity.