Case Report: Infant with prenatally diagnosed arachnoid cyst

Case This patient’s central nervous system abnormality was first suspected during a routine prenatal ultrasound at 29 weeks gestation. It was discovered that the patient had ventriculomegaly and a pineal region cyst (Figure 1a). A fetal MRI was performed at 31 weeks gestation (Figure 2). This showed a 3x3x3 cm unilocular cyst in the quadrigeminal plate cistern causing obstructive hydrocephalus. The fourth ventricle was normal in size. The corpus callosum was fully formed. No other anomalies were found. A repeat fetal ultrasound was performed prior to birth (Figure 1b).