cavum vergae fetal ultrasound

The septum pellucidum forms the medial walls of the lateral ventricles. It extends from the corpus callosum to the columns of the fornix. This area of the brain is variable. If it becomes large and wide during organogenesis, there will be only one cavum, cavum septi pellucidi. If this space is narrow, two cavities will form. The anterior one would be cavum septi pellucidi and the posterior, cavum vergae. Both of them are connected via the acqueductus septi.

In case the hind portion of the cavum septi pellucidi is separated from the front by the mutual contact between trigona and the corpus callosum, the two cavi will be isolated. Certain authors, consider cavum vergae as a part of the cavum septi pellucidi.

Cavum septi pellucidi and cavum vergae consist of two thin laminae of the white matter surrounded by gray matter with a potential intervening space. The leaves are separated in utero. They fuse from back to front as the fetus approaches term or within the first few weeks after birth. The cavum septi pellucidi persists when the two leaves fail to fuse. Cavum vergae obliterates first and the cavum septi pellucidi follows.  From this reason, existence of the cavum vergae on it”s own is unlikely. However, such cases have been documented, which suggests that the embryologic development in this region may not always occur in the usual sequence.

Persistence of the cavi is considered as a normal variant due to its frequent occurence. No specific clinical syndrome are described in connection with persistence of the cavi. The recent studies suggest that the enlarged cavum septi pellucidi serves as a significant marker of cerebral dysfunction manifested by neurodevelopmental abnormalities, while the cavum vergae alone does not identify individuals at risk for any cognitive delays.

The two following case represent an enlarged cavum vergae diagnosed in the third trimester.