Rhombencephalosynapsis - isolated anomaly or complex malformation?

Background: 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/methods: 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.

Results: 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.

Conclusions: Rhombencephalosynapsis has a very characteristic appearance on magnetic resonance imaging which allows diagnosis of this malformation at any age, including prenatal period.