Third-trimester Ultrasound Evaluation of Arachnoid Cysts

Abstract

Case 1. A 28-year-old primigravida was referred to the hospital at 34 gestational weeks because of an intracranial cyst. Two-dimensional ultrasound revealed a 1.76 × 2.69 cm midline interhemispheric hypoechoic homogeneous lesion that was consistent with an arachnoid cyst (Figure 1). The cystic mass was located behind the thalamus and above the cerebellum. There was no ventriculomegaly or midline shift. The cerebral sulci, gyri, and corpus callosum were normal. A 2,656-g female baby was delivered at term with Apgar scores of 10 at both 1 and 5 minutes. Postnatal magnetic resonance imaging (MRI) confirmed the prenatal diagnosis. The infant was healthy at the age of 18 months without any symptoms involving the central nervous system.