Preface to the Fourth Edition

Turning the pages of this fourth edition of Ultrasonography of the Fetal Brain, several thoughts come to mind. The first and most obvious one is that there have been impressive developments in the field of fetal neurosonography in recent years. The second, and to us the most intriguing one, is how the scope of the research in this area has changed with time. In the beginning, the ambition of the fetal sonologists was a simple one: to recognize neural tube defects. Later, it became clear that more subtle intracranial anomalies could be identified. At that point, it became clear that little was known about the prognosis of many of these conditions, and that counseling couples was a very difficult, sometimes even impossible, task. The intracranial anomalies that were detected could be associated with significant neurologic compromise; however, at the same time they could be completely asymptomatic. This standoff prompted a wave of studies to evaluate the postnatal development of infants diagnosed with abnormal cerebral anatomy in utero, as well as to identify the sonographic features that could make a difference in their outcome. The brain is in many ways an unexplored organ, and sonologists understood that not only was long-term follow-up necessary to obtain meaningful data, but also that intellectual function cannot be measured as easily as blood pressure or cardiac output. However, the wealth of data that continues to be generated by these studies is providing a significant contribution not only to prenatal diagnosis but to the entire field of fetal and pediatric neurology. In many ways, this bootstrapping process (recognizing anomalies while delineating their clinical implications) was at the forefront of a new type "backward medicine," that, for good or bad, is here to stay, as the side product of the widespread use of diagnostic imaging: predicting the consequences of abnormally shaped organs in asymptomatic individuals the complete opposite of traditional medicine.

Prenatal sonography of cerebral anomalies has found a powerful ally in magnetic resonance, and modern genetics provides fundamental information in many, although certainly not all, cases (one must remember that about one-third of these anomalies are not the consequence of abnormal embryogenesis but rather of destructive processes such as infection, ischemia, hemorrhage).

Our aim with the fourth edition of Ultrasonography of the Fetal Brain was to provide the best available information on all these different aspects. Following the tradition of our book, which has become the standard reference in the field, this new edition has been thoroughly updated. Some chapters are completely new, others have been significantly updated, and better quality images have been placed in many chapters.

There are many different ways to compile a medical textbook. Ultrasonography of the Fetal Brain is distinctive because the various authors came together from different parts of the world and collaborated in close relationships, writing in groups, co-writing, co-editing, and reviewing each other's work. As in previous editions, our aim was to provide a textbook that is exhaustive and at the same time easy to read.

One last remark. Now that the book is completed, we feel that the title Ultrasonography of the Prenatal Brain is no longer adequate. When reading the text, you will quickly realize that it contains much more than just straightforward ultrasonography. If in the future we have the opportunity to undertake a fifth edition, the new title probably should be Fetal Neurology.