Thinned Cavum Septum Pellucidum Leaflets Mimicking Septal Agenesis on Sonography

Abstract Background: Visualization of the cavum septum pellucidum (CSP) during the second and third trimesters is an important marker of normal central forebrain development. Nonvisualization of the CSP on prenatal ultrasonography raises concern for septal agenesis and associated neurodevelopmental abnormalities. However, markedly thinned CSP leaflets may mimic true agenesis.