Prenatal sonographic diagnosis of a suprasellar arachnoid cyst.

A 30-ycar-old gravida 2, para 2, woman was referred for ultrasound examination to detcmnine gestational age. A single fetus was seen or approximately 32 weeks. as dated by bipariatal diameter and femur length . A rounded midline cystic structure was seen in the fetal head. It was localized in the suprasellar region h>• hoth sagittal and it-..ial cuts and me<t'lured 3.5 cm in dimneter. No hydrocephalus was noted and the third ventricle was not clearlv identified. The other intracrnnial anatomic structures· were considered normal (figs. 1 and 2). The rest of the ohstetric sonogram was unremarkable. A repeat sonogrnm was done three weeks later. The cystic intracranial lesion had enlarged and measured 4 cm in diameter. Additionally, hydrocuphalus was seen. Mild polyhydramnios wa.'l also present. A presumptive diagnosis of an arachnoid suprnsellar cyst was made. Amniocentesis was done at 36 weeks• ,gestation confirming lung, maturity or the fetus. A week later a male infant \\ ~ lS horn by induced vaginal delivery. The newhorn weighed 2650 g with Apgar scores of 9 and 10 at one and five minutes, respectively. Head circumference was 35 cm, A computed tomographic {CT) scan of the head. done on the second day of life, disclosed hydrocephalus as well as a rounded 111cency of cerebrospinal rluid (CSF) density in the region of the third ventricle which measured 4.3 cm in diameter. The chardcteristic "head of the bunny .. appearance seen on CT scan and cranial sonograph~ · was consistent with the prenatal diagnosis (fig. 3). A solitary seizure was noted on the third day or life. A cystoperitoneal shunt procedure was performed on the nineteenth day of life. There had been a delay in operation since the infant developed neonatal sepsis. At surgery, a catheter was introduc.oed into the cyst. The wall of the cyst was thick, and the flow of fluid through the catheter was measured at a pressure of9 cm of water. The fluid analysis resembled that of CSF. The procedure was uncomplicated.