Prenatal and postnatal follow-up of a fetal interhemispheric arachnoid cyst with partial corpus callosum agenesis, asymmetric ventriculomegaly and localized polymicrogyria. Case report.

We report a case of a fetal interhemispheric arachnoid cyst associated with partial callosal agenesis and asymmetric ventriculomegaly. After second trimester ultrasound diagnosis and evaluation, magnetic resonance imaging (MRI) at 28 weeks showed polymicrogyria laterally to the cyst. The parents decided to continue the pregnancy. The diagnosis was confirmed after birth by transfontanellar ultrasound examination and MRI. In the neonatal period, the child was sleepy and showed axial hypotonia. At 1 month of age, he had a normal neurological examination. Cyst-peritoneal shunting was performed at 5 weeks of age because the cyst increased markedly in size, and shunt revision was required at 8 months of age. At 17 months, he had mild left-side hemiparesis but he could walk alone and had begun to speak. To date, the child never experienced seizures. We review other published cases and discuss the postnatal outcome of this rare association.