Septo-optic dysplasia (SOD; De
CASE REPORTS
Case 1A healthy 17 year-old primigravid woman was referred at 29 weeks of gestation on suspicion of fetal holoprosencephaly. Sonographic examination, using an Aloka 5500 (Aloka, Decines Charpieu, France) ultrasound machine equipped with 6-MHz abdominal and transvaginal probes, revealed isolated absence of the septum pellucidum (SP): the lateral ventricles had square fused frontal horns (Figure 1). There was no ventriculomegaly, the thalami were not fused, and the corpus callosum, fornix, anterior cerebral artery and falx cerebri were normal, thus excluding holoprosencephaly (Figure 2). Cerebral gyration appeared normal for gestational age, the Sylvian fissure and callosomarginal, central and temporal sulci all being observed. Fetal MRI confirmed the sonographic findings and showed hypoplasia of the optic chiasma (Figure 3). There was no evidence of cortical dysplasia. The possibility of septo-optic dysplasia (SOD; De Morsier syndrome) was raised and maternal serum and urinary estriol tests were performed, which revealed very low levels. Since estriol arises from placental aromatization of androgens of fetal adrenal origin 1 , these low levels were consistent with the diagnosis of fetal adrenal insufficiency, probably secondary to adrenocorticotropic hormone (ACTH) deficiency and hypopituitarism. These biological results, along with the ultrasound and magnetic resonance imaging (MRI) findings, were consistent with the diagnosis of fetal SOD but the mother refused cordocentesis for further fetal endocrine assessment. Despite counseling about a poor outcome, she did not ask for a termination of pregnancy, which would have been permitted, according to French law, and a full-term 2960-g male infant was delivered. Postnatal investigations ascertained the diagnosis of SOD with hypopituitarism and blindness. The infant had growth hormone, ACTH and thyroid stimulating hormone deficiency. At the time of writing the child was 4 years old, and was developmentally delayed and blind.
Case 2A healthy 31 year-old primigravid woman was referred for a first sonogram at 30 weeks of gestation when her pregnancy was discovered. On sonography only the very anterior part of the SP was seen, with no posterior part, the frontal horns being fused at this level (Figure 4). The atrium of the lateral ventricles was 10 mm wide. Holoprosencephaly was ruled out since the corpus callosum was normal in length (37 mm), and the anterior cerebral arteries, the columns of the fornix and the falx cerebri were also normal. The gyration was normal for gestational age. The optic nerves were 3 mm in diameter, which is standard for this gestational age. There was no microcephaly nor dysmorphic features. The
