Normal IQ in a 55-year-old with newly diagnosed rhombencephalosynapsis.

Rhombencephalosynapsis (RS) is a rare congenital disorder characterized principally by agenesis/hypogenesis of the cerebellar vermis and fusion of the dentate nuclei and cerebellar hemispheres. Fusion of the peduncles and colliculi is common, and associated anomalies of the cerebral hemispheres also can be present. Only about 50 cases with RS have been described and the majority of these have been children. While the literature suggests that RS often is associated with behavioral and/or intellectual impairment, no previous report has described overall neuropsychological functioning. This report describes an employed male who was diagnosed with RS by MRI at age 55. The neurological examination revealed only subtle sensory-motor abnormalities and the results of the neuropsychological evaluation were generally within normal limits, with the exception of poor immediate visual memory and motor dexterity. These findings suggest RS is not inevitably associated with substantial cognitive impairment.