Truncal ataxia, hypotonia, and motor delay with isolated rhombencephalosynapsis.

We report on a 16-month-old girl with developmental motor delay, microcephaly, and mild truncal ataxia who was revealed to have rhombencephalosynapsis on magnetic resonance imaging. The child was nonsyndromic and exhibited normal cognitive and social abilities for her age, despite neuroimaging findings. As this case demonstrates, motor skills in children with isolated rhombencephalosynapsis may be relatively mildly affected, and cognition may be normal despite the presence of a major central nervous system anomaly. Neuroimaging may be helpful in defining the nature of a child's deficits at an early age, particularly when associated with microcephaly and abnormalities on neurologic examination.