Vesicular swelling in the cervical region with lymph sac formation in human embryos

Abstract

Vesicular swelling in the cervical region (VSC) is occasionally observed among human embryos around Carnegie stage (CS) 21. However, its mechanism and significance in fetal development are unclear. The present study aimed to analyze the relation of development of VSC with jugular lymph sac (JLS) formation. Serial histological sections that were digitalized from 14 embryos at CS20 and CS21 stored at the Kyoto Collection were used for the analysis. Subcutaneous edema and enlargement of the subarachnoid space were found to cause VSC. No obvious abnormalities in cranial regions that may be related to the VSC were detected on histological sections. Three‐dimensional reconstructions revealed the following: (a) the JLS was located bilaterally at the levels between the first and fourth cervical vertebrae; (b) the JLS was pyramidal in shape; and (c) no severe deformity and/or malformation was found in all samples. The JLS was not connected to the subcutaneous tissue and subarachnoid space in all samples. The mean volume of the JLS increased nine‐times from CS20 (0.02 mm3 in VSC [−] group) to CS21 (0.18 mm3 in VSC [−] group). The mean volume of the JLS was comparable between the VSC [−] and VSC (+) groups at both CS20 and CS21. A moderate correlation was observed between VSCd and the mean volume of the JLS in both groups at CS20 (R2 = 0.75) and CS21 (R2 = 0.56). In conclusion, the dynamics of the lymphatic system at the cervical region may contribute to VSC observed around CS21. © 2019 Japanese Teratology Society

Three-dimensional reconstruction of lymphatics using a crown-rump length 30 mm human fetus

“…The left JLS (2.53 mm 3 ) was larger than the right JLS (1.93 mm 3 ). These results indicated that our results were slightly different than those of Carnegie stages 20 and 21 [10] .…”

Does the presence of extended jugular lymphatic sacs add more risk to nuchal thickness for genetic and structural abnormality?

“…[ 3 - 10 ] The most widely accepted theories to explain the NT increase are cardiac dysfunction/failure or venous congestion in the fetal head and neck,[ 9 ] alterations in extracellular matrix components,[ 10 ] conditions such as fetal anemia, infection, and hypoproteinemia,[ 11 ] and disorders of lymphangiogenesis. [ 12 ] However, these theories could not explain the reason for the localization of such thickening to the neck of the fetus or the transient nature of this finding. It has also remained unexplained why concomitant EJLS appeared simultaneously in some cases and not in others.…”