Prenatal magnetic resonance imaging of atypical partial rhombencephalosynapsis with involvement of the anterior vermis: two case reports

Rhombencephalosynapsis is a hindbrain malformation characterized by complete or partial absence of the cerebellar vermis, with varying degrees of midline continuity of cerebellar hemispheres, dentate nuclei, and in some patients of the superior cerebellar peduncles. Partial rhombencephalosynapsis usually consists of a segmental deficiency of posterior vermis. Although prenatal diagnosis of rhombencephalosynapsis is feasible by ultrasound and magnetic resonance imaging both, partial rhombencephalosynapsis might be difficult to detect, especially at an early gestational age. We report two fetal cases of atypical partial rhombencephalosynapsis, with deficiency of anterior vermis, detected by prenatal magnetic resonance imaging at 21st and 23rd week of gestation, respectively.