Prenatal diagnosis of rhombencephalosynapsis and postnatal outcomes associations and outcomes of prenatally detected rhombencephalosynapsis

ObjectiveTo describe the association between prenatal imaging and neurodevelopmental outcomes of fetuses with rhombencephalosynapsis (RES).Study designThirty-four pregnancies complicated by RES were identified from our institutional databases based on US and/or MRI findings. Genetic testing results were gathered. In cases of termination of pregnancy, we studied the association between prenatal imaging and neuropathologic findings. For those who opted for expectant management, comprehensive developmental assessments and postnatal MRI imaging were evaluated.ResultsOver one third of fetuses in our cohort had complete RES. Common intracranial anomalies identified were mesencephalosynapsis, aqueduct stenosis and diencephalosynapsis. The degree of RES was not associated with the frequency of additional central nervous system anomalies. MRI had a good correlation with neuropathologic findings with regard to the degree of RES, aqueduct stenosis and mesencephalosynapsis. Postmortem autopsy showed that one third of our cases had VACTERL-H and almost all of those had complete RES. All liveborn neonates(n = 6) had aqueduct stenosis requiring ventriculoperitoneal shunting within days of delivery (median 5 days). While a large proportion of prenatally suspected complete RES were found to have partial RES on postnatal imaging, prenatal diagnosis of aqueduct stenosis remained unchanged. All children that were at least 2 years old (n = 3) had global developmental delay.ConclusionPrenatal assessment of the RES severity is challenging and may be unreliable. Nevertheless, postnatal prognosis is poor for both complete and partial RES. Associated aqueductal stenosis, can be reliably assessed prenatally and this may contribute to worse postnatal prognosis than the degree of RES. What is already known about this topic? Rhombencephalosynapsis (RES) is a rare cerebellar abnormality which is characterized by midline fusion of the hemispheres with partial or complete loss of the vermis. Assessing the severity of RES postnatally is important as children with complete RES exhibit overall poorer outcomes than those with partial RES.What does this study add? A large proportion of prenatally suspected complete RES were found to have partial RES on postnatal imaging (80%). Precise assessment of the degree of RES prenatally is challenging and may be unreliable. However, associated anomalies, especially aqueduct stenosis, can be reliably assessed prenatally. Regardless of the imaging severity of RES, all neonates with associated aqueductal stenosis required ventriculoperitoneal shunting in the first month of life and exhibited global developmental delay at 2 years of age.