EP05.36: Association of prenatal conatal cysts with structural and genetic anomalies

Conatal and subependymal cysts are two different entities regarding etiology and prognosis frequently confused during fetal life. Conatal cysts are traditionally considered as benign while subependymal are related to neurological damage, genetic anomalies or infections. Most of the previous literature include few cases and analyse these 2 conditions together. The objective of this study is to evaluate prenatal conatal cysts association with structural and genetic anomalies and postnatal results. Retrospective study including cases of prenatal conatal cyst diagnosed in our neurosonography unit from January 2016-December 2023. Data recorded included associated anomalies (intra- or extracranial findings), chromosomal microarray (CMA) and postnatal evolution. We included 13 fetuses with a median gestational age at diagnose of 32 weeks (IQR 26-35). 7/13 cases had no other structural anomalies, 1/13 presented moderated macrocephaly (cephalic perimeter +2.6SD), 4/13 presented minor extracranial findings (mild pyelocaliceal dilatation, clubfoot, and mild polyhydramnios), 1/13 auricular flutter and 1/13 a left diaphragmatic hernia. MRI was performed in 9/13 cases confirming ultrasound findings. In 12/13 an amniocentesis was performed; with negative results for infection (cytomegalovirus (CMV) and toxoplasma); and normal CMA in 10/12, one case associated to macrocephaly presented a duplication of 16Mb in 12p13 associated to motor and neurological delay who decided to TOP; and the other with fetal arrythmia with a deletion of 5.5Mb in 7q21 inherited from the mother classified as VOUS finding. All neonates had a normal result, except for the diaphragmatic hernia in which postnatal Simpson-Golabi-Behmel syndrome was diagnosed. Posterior follow-up was available for 8 patients, with normal development until now (3 months-5 years of life). Isolated conatal cysts have normal postnatal outcomes, our results reinforce that conatal cysts are a benign condition and suggest that complementary studies should be reserved for those cases with associated anomalies.