Dilated cavum septi pellucidi in fetuses with microdeletion 22q11.

OBJECTIVES

The cavum septi pellucidi (CSP) is an easily recognizable landmark in the fetal brain. CSP disappears after birth to form the septum pellucidum. Children with microdeletion 22q11 (del. 22q11) were, however, reported to have a persistent dilated CSP. This study was designed to examine whether the CSP is dilated in fetuses with del.22q11.

METHODS

This was a case-control study where the CSP width was measured in normal fetuses from 16 to 34 weeks and in fetuses with del. 22q11. CSP width was correlated to the biparietal diameter (BPD). Reference curves were constructed, and z-scores calculated.

RESULTS

Cavum septi pellucidi width in 260 normal fetuses showed a linear correlation with BPD. The study group consisted of 37 fetuses with del. 22q11. In 25/37 (67.5%) of fetuses with del. 22q11, the CSP was enlarged with a mean z-score of 2.64 (p < 0.0001). Fetuses with a BPD > 50 mm (>22 weeks of gestation) had a dilated CSP in 85.7% (24/28).

CONCLUSIONS

The CSP is a structure routinely evaluated in screening ultrasound. A wide CSP is found in second trimester fetuses with del. 22q11. A dilated CSP may be an important sonographic marker for the presence of del. 22q11 along with conotruncal malformations and thymic hypoplasia. © 2016 John Wiley & Sons, Ltd.