Brain malformations and fetal ventriculomegaly: What to look for?

Early, sensitive and specific prenatal diagnosis of malformations of the fetal brain and correct identification of the various etiologies of ventriculomegaly are essential for the pre-, peri-, and postnatal management. Prenatal ultrasonography (US) is the primary imaging modality for identification of fetal central nervous system (CNS) pathology. However, prenatal US may not always identify the full spectrum of pathology. Consequently, the final diagnosis may be incorrect or underestimate the CNS anomaly. Fetal magnetic resonance imaging has emerged as a valuable, safe and easy to perform secondary imaging tool for the evaluation of the fetal CNS. The high spatial resolution, good signal to noise ratio, and high contrast to noise ratio allow the study of various developmental processes of the fetal CNS in detail. Consequently, fetal magnetic resonance imaging may show pathology that remained undetected on prenatal US. The extra information has proven invaluable for managing these high-risk pregnancies and is also important for the counseling of the parents. In the current review we discuss various frequently encountered brain malformations as well as the various etiologies of "ventriculomegaly".