Résumé
Aim: contribute to a better understanding of isolated fluid enlargement in terms of prenatal diagnosis and postnatal outcome, and identify ways to improve prenatal counseling.Materiel and methods: retrospective, bicentric study of all cases of antenatal diagnosis of isolated fluid enlargements of the posterior cerebral fossa, from January 2010 to April 2022. They were classified as mega cisterna magna, arachnoid cyst, or Blake's pouch cyst. Children's postnatal development was collected with a maximum follow-up of 12 years on the basis of pediatric neurology and neurosurgery consultations, and children's health records. Patients were classified into 2 groups: normal development and delayed psychomotor development.Results: 53 children were included, including 21 with mega cisterna magna, 20 with arachnoid cysts and 12 with Blake's pouch cysts. There was a male predominance, with 65% of male fetuses. Arachnoid cysts were significantly associated with higher cistern magna measurements, distal elevation of the cerebellar tent and more mass effect on the vermis on antenatal imaging. Postnatal imaging normalized in 8 children (16%). 43 children (86%) had normal neurological development. 7 children showed an overall delay in psychomotor development. Of the arachnoid cysts monitored, 3 children (15%) underwent surgery in the first year of life, due to the onset of hydrocephalus.Conclusion: our study highlights the favorable prognosis of isolated fluid enlargements. Advances in antenatal imaging have allowed us to classify them more precisely and provide parents with more accurate information. However, a postnatal imaging and a detailed clinical evaluation should be carried out, especially for children with arachnoid cysts at risk of developing hydrocephalus.