Outcome of Fetuses With Abnormal Cavum Septi Pellucidi: Experience of a Tertiary Center

Background: Cavum septi pellucidi (CSP) is easily evaluated in the second and third trimester of the pregnancy. The structure is an important feature of the standard planes used for routine morphological assessment of fetal head and central nervous system (CNS): trans-thalamic and trans-ventricular plane. The standard description of the CSP is an anechoic rectangular box between two hyperechoic lines represented by the septum pellucidum. The pathological aspects are mainly represented by the absence of its normal appearance, which is associated with severe CNS malformations of the brain midline as corpus callosum agenesis, hydranencephaly, porencephaly, schizencephaly, holoprosencephaly, syntelencephaly or severe chronic hydrocephaly. Other issues such as increased or reduced dimensions of the CSP are not considered significant if found isolated, although the fetal genetic investigation is suggested by some authors. The objective of the study was to evaluate the outcome of fetuses with abnormal CSP detected by sonography in the last 5 years, in the Prenatal Diagnosis Unit (PDU) of our tertiary center. Methods: We performed a retrospective review of the cases with abnormal CSP evaluated in our tertiary unit, diagnosed between January 2012 and November 2016. The fetal anatomy was evaluated in all cases following the recommendations of the international guidelines. In abnormal CSP cases, fetal neurosonogram and an extended fetal anomaly scan were performed and amniocentesis was proposed to identify genetic disorders. Results: A total of 7,520 cases were examined for morphological purposes and abnormal CSP was found in 36 cases. Absent CSP was the initial observation that triggered further investigation and diagnosis in the cases with agenesis of corpus callosum (ACC) (seven cases) and septo-optic dysplasia (two cases). In hydranencephaly or severe hydrocephaly, porencephaly, schizencephaly and holoprosencephaly, the heavily malformed aspect of the brain is obvious, and the absence of CSP is only an observation, with less diagnostic importance and clinical implications. Partial or total ACC was mainly associated to absent CSP, as the development of two structures is merged. Almost half of the total abnormal CSP cases (16/36) were associated with genetic disorders, most of them with abnormal karyotype and all of them were associated with the absence of CSP. The persistent enlargement of CSP (4/36 cases) and the hyperechoic aspect of CSP (1/36) were not associated with other structural or genetic abnormalities and the postnatal neuromotor development was normal. Conclusions: The CSP evaluation is mandatory and normal aspects suggest a normal development of the midbrain. Genetic testing should be offered especially for the cases with absent CSP because of the high incidence of chromosomal disorders. As the absence of CSP is associated with severe structural or genetic disorders, its visualization in the second half of pregnancy is mandatory for any anomaly scan. The enlargement and echogenicity variations of CSP associate a favorable neonatal outcome. However, long-term follow-up is recommended in the apparently normal neonates and infants, as they may develop abnormal psychological behavior lately. J Clin Gynecol Obstet. 2016;5(4):112-116 doi: https://doi.org/10.14740/jcgo423w