Page 42 - SONO 260 The Fetal Head and Brain

CEREBRAL MALFORMATIONS DANDY-WALKER MALFORMATION & MEGA CISTERNA MAGNA
¢ Mega cisterna magna, which is the enlargement of the cisterna magna without the involvement of the fourth ventricle, may be confused with Dandy-Walker malformation.
— Mega cisterna magna is present when only the cisterna magna is enlarged, measuring more than 10 mm in depth.
— Consequently, the fourth ventricle is normal with mega cisterna magna and enlarged with DWM.
— It is important to note that in the early second trimester, the inferior portion of the cerebellar vermis may not be formed, thus making it appear as if the fetus has partial agenesis of the vermis.