FIG 1. Case 1. Serial sonographic images, an MR image, and an angiogram show a DSM.

A, Transvaginal sonogram at GA 8 weeks shows the 15-mm-long fetus.

B, Sonogram at GA15 weeks 5 days. Arrow indicates the head. Crown-rump length is 87 mm.

C, Sonogram at GA 23 weeks 6 days definitively shows a huge cystic lesion (arrow).

D, MR image at GA 37 weeks 5 days shows a huge dural lake in the posterior fossa with signal intensity void.

E, Right common carotid angiography (lateral view) shows a dural lake (asterisk) fed by tentorial artery (arrow), middle meningeal artery, and occipital artery.