[Unilateral aplasia of the cerebellum in Aicardi's syndrome].

A case of unilateral aplasia of the cerebellum in a girl with Aicardi's syndrome is described. Aplasia of an entire hemisphere is one of the least frequent malformations of the cerebellum. Hypoplasia, partial hemispheric defects of the cerebellum and, rarely, complete absence of one hemisphere have been described in Aicardi's syndrome, which is associated with multiple systemic and CNS malformations. In our patient, who presented the characteristic trial of infantile spasms, callosal agenesia and retinal lacuna, we also saw right cerebellar aplasia along with other CNS malformations using magnetic resonance. We discuss the possibility that this aplasia arises as the result of a developmental defect of the posterior arterial system of Willis's polygon.