Rare case of rhombencephalosynapsis (RES); Case report and literature review

• This article highlights a rare posterior fossa malformation, rhombencephalosynapsis, occurring consequent to embryological insult and presenting either in isolation or as a constellation of CNS or extra CNS abnormalities. • This case study details a young adult who underwent MR because of his unusual behavior, revealing rhombencephalosynapsis with an absent inferior cerebellar vermis, midline continuity of the cerebellar hemisphere and fused dentate nuclei. • He was managed with supportive care, psychiatric evaluation and comprehensive counseling. The absence of the vermis and the continuity of the cerebellar hemispheres, dentate nuclei, and superior cerebellar peduncles are the hallmarks of rhombencephalosynapsis, a congenital disorder of the cerebellum. It has varying degrees of neurological damage and can occur as a single aberration (rare) or as a component of a larger brain malformation. We present a case of a young adult with two year history of unusual behaviors and falls, who on MRI was diagnosed with rhombencephalosynapsis. Our case demonstrates the common characteristics of RES and the critical function of MRI in diagnosis and treatment.