Prenatal ultrasound diagnosis of neural tube defects. Pictorial essay.

Neural tube defects (NTD) are a heterogeneous group of malformations resulting from failure of normal neural tube closure before the fourth and fifth week of embryologic development. The three most common forms of NTD are: anencephaly, encephalocele and spinal dysraphism. Less common forms of neural tube defects include iniencephaly, amniotic bands and other types of spinal abnormalities including scoliosis/cyphosis, sacral agenesis, limb-body wall complex, diastematomyelia. The most part of these abnormalities are accessible to the ultrasound diagnosis in the midtrimester and sometimes even in the late first trimester of the pregnancy. This kind of abnormalities can occur in isolation or in association with other anomalies, which can also be characterized with ultrasound. In this pictorial essay the ultrasonographic aspects of the NTD will be discussed.