Female, 23 years old, with di-di twin pregnancy, 32 week 6 day GA, midline brain cyst seen on twin A on ultrasound. Imaging was tailored for assessment of twin A which lies more caudally and more toward the maternal left. Brain parenchymal morphology and signal characteristics of twin A are within normal limits for gestational age. A normal cavum septum pellucidum is identified. More posteriorly, a slightly prominent cystic space is seen situated at midline, just below the splenium of the corpus callosum and above the internal cerebral veins. No other definite abnormal fluid collections are seen. Twin B is inadequately assessed due to excessive fetal motion, but the limited images obtained show no significant abormality. Maternal pelvicaliectasis is seen on the left, likely physiologic.
A slightly prominent cystic space is seen in twin A situated between the splenium of the corpus callosum and the internal cerebral veins. This is a typical location for a cavum vellum interpositum, sometimes referred to as a cyst of the cavum vellum interpositum. The brain is otherwise within normal limits for gestational age. Please note that this exam was interpreted without the benefit of review of the prior US images. These will be obtained and reviewed, and if any change to the interpretation is warranted, an addendum to this report will be made. 