EMBRYOLOGY OF ECTOPIA CORDIS

AND PENTALOGY OF CANTRELL

The sternum arises from two parallel bands formed from longitudinal fusion of the mesenchymal layers. Early in the 6th week, the sternum is represented by concentrations of mesenchyme in two parallel primordia, the sternal bars, at some distance from the midline. The sternal bars become progressively chondrified and move towards the midventral line, fusing with each other from the cephalad to caudal ends, forming a median cartilaginous plate (1).

Failure of sternal fusion results in a variety of cleft sternal disorders, ranging from complete to partial ectopia cordis (2).

The mechanism of this failure and the appearance of associated diaphragmatic and heart anomalies in such cases are unknown.

Several forms of sternal cleft exist, with the common pathological finding being partial or complete displacement of the heart from the thorax. This, in nearly all cases is associated with a midline defect of the body wall at some point.

REFERENCES

1. Achiron R, Schimmel M, Farber B et.al. Prenatal sonographic diagnosis and perinatal management of ectopia cordis. Ultrasound Obstet Gynecol 1991;1:431-434.
2. Miller RM. Birth defects. In: Bergsman, D (ed). Compendium, 2nd edn, New York; Alan R Liss:382-383.