Rhombencephalosynapsis – isolated anomaly or complex malformation?

Rhombencephalosynapsis (RES) is a rare malformation of the posterior cranial fossa, characterized by fusion of the cerebellar hemispheres, medial cerebellar peduncles and dentate nuclei. Over the period of 7 years 8 cases of this anomaly have been diagnosed in two pediatric centers in Warsaw including one on the prenatal magnetic resonance imaging (MRI). Material consists of involves one fetus examined at the gestational age of 27 and 33 weeks and 7 children (5 girls and 2 boys) aged 8 months – 16 years. All of them underwent brain MRI with the use of 1.5T scanners. In 1 case RES was an isolated anomaly, in 1 case it was accompanied by hydrocephalus only, in the remaining 6 cases RES was an element of a complex malformation. The additional anomalies were as follows: callosal hypoplasia in 3 children, abnormalities of gyration in 2, brainstem hypoplasia in 2, isolated fourth ventricle in 1, abnormal white matter signal intensity in 4 (in 2 cases in supratentorial compartment, in 1 in the cerebellum and in 1 in the pons), abnormally dilated extraaxial fluid collections in 2, syringohydromyelia in 2. In 5 cases RES was total, in 3 – partial. Rhombencephalosynapsis has a very characteristic appearance on magnetic resonance imaging which allows diagnosis of this malformation at any age, including prenatal period