Prenatal hydrocephalus: Prenatal diagnosis

Abstract

This chapter comprises three parts: (1) embryology of the central nervous system, (2) normal ultrasound appearance of the brain from the embryonic period to term of pregnancy, and (3) ultrasound prenatal diagnosis of primary and secondary ventriculomegaly/hydrocephalus. In particular, the first part of the chapter represents a thorough description of the early development of the brain in the human fetus, including an interesting sono-anatomic correlation since when the embryonic brain can be explored with ultrasound, i.e., from the 7th gestational week. The second part is meant to illustrate to non-experts in fetal neurology how ultrasound is able to follow the dramatic changes in the brain appearance and anatomy due to the various phases of cerebral development (from the normally lissencephalic brain of the 2nd trimester to the 3rd trimester process of neuronal proliferation and migration). The last part describes in details the diagnostic criteria to establish in the fetus a diagnosis of primary (aqueductal stenosis) versus secondary ventriculomegaly, the latter related to a wide range of genetic and developmental disorders.