Agenesis of cerebellum associated with arrhinencephaly.

Complete cerebellar agenesis or aplasia is an extremely rare condition with few previously reported cases. We identified a 38-week gestation infant with microcephaly who had complete cerebellar agenesis associated with arrhinecephaly. There was complete lack of the efferent and afferent limbs of the cerebellum, including the nuclei of the basis pontis, the inferior olivary nuclei, ascending spinal and medullary afferents, deep cerebellar nuclei and their afferents, and the red nucleus. Although complete cerebellar agenesis is rare, cerebellar hypoplasia is more common and can be sporadic, asymmetric, or represent clinically, genetically, and pathologically diverse examples of primary cerebellar or vermian hypoplasia.