OP07.01: Clinical significance of isolated posterior fossa anomalies: Dandy-Walker variant, megacisterna magna and Blake's pouch cyst

Abstract

To determine the outcome of fetuses with a prenatal ultrasound (US) diagnosis of isolated Dandy-Walker variant (DWV), megacisterna magna (MCM) or Blake's pouch cyst (BPC). Registers from our scan database diagnosed as isolated posterior fossa (PF) anomaly between 2002 and 2008 were retrospectively collected at Vall d'Hebron Materno Infantil Hospital in Barcelona. Information concerning karyotype, other image studies, pathology findings, perinatal outcome and postnatal evaluation was obtained from medical records. Infant's development and behaviour was evaluated with the validated tool parent's evaluation of development status (PEDS). This series included 24 cases over seven years, we sonographically identified 7 fetuses with isolated DWV, 14 with isolated MCM, and 3 with isolated BPC. Mean gestational age at diagnosis was 24 weeks for DWV, 29 weeks for MCM and 20 weeks for BPC. Karyotypes were performed in 4, 8 and 2 fetuses with DWV, MCM and BPC respectively and all were normal. Of DWV cases 4 (57.4%) requested termination of pregnancy (TOP), one was lost after diagnosis, one had an intrauterine fetal demise and one had a healthy neonate. Of MCM cases one opted for TOP and 13 continued, all healthy neonates were born uneventfully, but one has developmental delay at follow-up. All cases of BPC continued pregnancies and finished with healthy babies. PEDS was used to detect possible developmental or behavioural problems in 16 cases with isolated PF anomalies in fetal US. We found one infant (6.2%) in group A-treatment needed; two infants (12.5%) in group B-perform wider evaluation; three infants (18.8%) in group C-close observation, and ten infants (62.5%) in group E-normal. Isolated DWV prognosis is still unclear, even when karyotype is normal, and both, isolated MCM and BPC, are generally associated to normal karyotype and have a high possibility of leading to a normal neonate and good long term prognosis.