Evaluation and Significance of Nonvisualization of the Cavum Septum Pellucidum on Prenatal Ultrasonography

ABSTRACT Importance The identification of the cavum septum pellucidum (CSP) is an integral part of the routine second trimester fetal anatomy scan. The absence or nonvisualization of the CSP has significant clinical implications and requires further evaluation and counseling for the pregnant patient. Objective The aim of this review is to review the importance of accurate sonographic identification of the CSP and the underlying pathologies that can be associated with nonvisualization of this structure. Evidence Acquisition A literature review was performed with PubMed using key words including CSP, fetal anatomy ultrasound, and fetal anomalies. Results The absence of the CSP is associated with several central nervous system pathologies, all with a wide range of phenotypic outcomes, ranging from normal to very severe or lethal. Relevance Most obstetrician-gynecologists will have a patient in whom a CSP is not identified on fetal ultrasound. Thus, it is imperative to have a general understanding of this relatively common entity. Target Audience Obstetricians and gynecologists, family physicians Learning Objectives After completing this activity, the learner will be able to describe the CSP, the importance of accurate identification on ultrasonography, and the pitfalls to avoid/be aware of; explain the additional workup required in the setting of absent CSP including utility of antenatal ultrasound, fetal magnetic resonance imaging, and genetic counseling; and discuss the various pathologies that have an association with the absence of the CSP and patient counseling regarding the absence of the CSP.