Sonography of the fetal neural axis: a practical approach

Abstract

Among serious fetal anomalies currently detectable with ultrasound, defects of the central nervous system (CNS) are among the most common. These congenital anomalies are especially likely to burden not only affected children with severely limiting handicaps, but also their families with long-lasting anguish and financial responsibility. It is appropriate that interest in methods for improving prenatal detection of these abnormalities has intensified. Alphafetoprotein screening programmes are now widely available, and many papers have been written describing useful sonographic observations that enhance prenatal diagnosis. As a consequence, the majority of the most common serious neural axis defects including fetal hydrocephalus, anencephaly, myelomeningocele and encephalocele, previously detected almost exclusively at birth, today can be accurately detected prenatally. A few observations in the fetal brain and spine have proven to be especially useful in this task. This article presents a simplified and effective approach to the general sonographic survey of the neural axis in fetuses at average and increased risk for these anomalies. The aim is to improve not only accuracy of diagnosis of CNS malformations, but the efficiency and confidence of the examiner.