MRI Demonstration of Supratentorial Developmental Abnormalities in Chiari II Malformation: Prognostic Implications in a Treated Myelomeningocele Patient

Chiari II malformation is typically associated with myelomeningocele and hindbrain herniation, but the contribution of supratentorial abnormalities to neurological outcome remains underemphasized. We report the MRI findings of a 10-year-old child with antenatally diagnosed myelomeningocele repaired at birth, presenting motor disability and epilepsy. Brain MRI demonstrated severe Chiari II malformation with marked tonsillar descent, small posterior fossa, and vermian dysplasia, associated with septum pellucidum agenesis, posterior corpus callosum dysgenesis, periventricular nodular heterotopia, and cortical organization abnormalities. Triventricular hydrocephalus with ventriculoperitoneal shunt and extensive closed spinal dysraphism were also identified. This case illustrates that MRI evaluation of Chiari II malformation should extend beyond the posterior fossa because supratentorial developmental abnormalities may substantially contribute to neurological impairment.