‘Pseudo-septum’ Appearance in Septal Agenesis on Fetal MRI

Abstract

Background Absence of the cavum septum pellucidum (CSP) can be associated with a wide spectrum of congenital brain malformations. It is necessary to describe the anatomic structures that can be mistaken for the CSP in cases of septal agenesis. Results We retrospectively studied MRI of 12 fetuses referred with suspicion of absent CSP on sonography. The structures simulating CSP in axial sections (Pseudo septum) are: volume averaging from the medial edge of the frontal lobes (lateral ventricles) in the anterior aspect, fornices in the mid and posterior aspect and internal cerebral veins in the postero-inferior aspect. Eleven out of the twelve suspected cases of absent CSP showed a false positive ‘pseudo-septum’ appearance in axial sections of fetal brain MRI. The absence of the ‘pseudo-septum’ was confirmed on coronal MRI sections of the fetal brain. Conclusion It is important to study the axial and coronal sections of the fetal brain for accurate diagnosis of septal agenesis.