Unusual MRI findings in rhombencephalosynapsis

Rhombencephalosynapsis is mainly characterized by fusion of the cerebellar hemispheres and vermian agenesis. We report severe cerebellar hypoplasia, p achygyria of the cerebrum, an isolated (trapped) fourth ventricle, and faci al hemangioma in association with this condition. Our findings suggested th at the frequency of rhombencephalosynapsis appears to be higher than previo usly thought (approximately 0.13%), and it should not be misinterpreted as Chiari II malformation. (C) 2000 Elsevier Science Ltd. All rights reserved.