Isolated absence of septum pellucidum: prenatal diagnosis and outcome.

Septal agenesis is a rare cerebral developmental anomaly characterized by partial or complete absence of the septum pellucidum (ASP). Septal agenesis may be associated with various congenital brain malformations, namely holoprosencephaly, septooptic dysplasia (SOD), schizencephaly or agenesis of the corpus callosum. Current imaging technologies do not enable differentiation in utero between isolated ASP and SOD. This is due to the fact that optic nerve hypoplasia and endocrine anomalies are never ruled out completely. We report a case of prenatal diagnosis of isolated ASP based on 2D and 3D ultrasound and fetal MRI. Postnatal MRI confirmed prenatal findings and the boy is currently doing well at 18 months of age.