Management Considerations for an Isolated Enlarged Cavum Septum Pellucidum: A Case Report

We present the case of a male infant identified prenatally with an isolated enlarged cavum septum pellucidum (CSP) on ultrasound with otherwise normal neuroanatomy. At 24 weeks and four days of gestation, an anatomy scan demonstrated a CSP measuring 7.5 mm (95th percentile). A repeat maternal-fetal medicine ultrasound at 26 weeks and four days revealed further enlargement to 9.3 mm. While the CSP size was above average, no other structural anomalies were identified. The parents were counseled on potential associations, including chromosomal abnormalities and neurodevelopmental disorders. The pregnancy and delivery were otherwise uncomplicated. At 17 months of age, the child has met or exceeded gross motor, fine motor, language, and social-emotional developmental milestones. This case emphasizes the importance of distinguishing isolated CSP enlargement from cases with additional anomalies, providing appropriate counseling, and ensuring postnatal developmental follow-up.