Magnetic resonance imaging (MRI) is now considered the imaging modality of choice for the majority of disorders affecting the central nervous system. This is particularly true for gray and white matter disorders, thanks to the superb soft tis sue contrast in MRI which allows gray matter, unmyelinated, and myelinated white matter to be distinguished and their respective disorders identified. The pre sent book is devoted to the disorders of myelin and myelination. A growing amount of detailed in vivo information about myelin, myelination, and myelin dis orders has been derived both from MRI and from MR spectroscopy (MRS). This prompted us to review the clinical, laboratory, biochemical, and pathological data on this subject in order to integrate all available information and to provide im proved insights into normal and disordered myelin and myelination. We will show how the synthesis of all available information contributes to the interpretation of MR images. After a brief historical review about the increasing knowledge on myelin and my elin disorders, we propose a new classification of myelin disorders based on the subcellular localization of the enzymatic defects as far as the inborn errors of me tabolism are concerned. This classification serves as a guide throughout the book. All items of the classification will be discussed and, whenever relevant and possi ble, be illustrated by MR images.

Clearly structured, each chapter describes: * clinical features and laboratory investigations * pathology * pathogenetic considerations * therapy * case presentation * MRI and spectroscopy of a specific myelin disorder Completely updated and expanded by 20 chapters to include the latest information on: - inborn errors of metabolism and neurodegenerative disorders - the role of subcellular structures - enzyme biochemistry - the pathophysiological mechanisms of posthypoxic-ischemic cerebral damage - inflammatory and infectious disorders Plus: Greater coverage of the genetic and pathophysiological mechanisms underlying white matter disorders. Finally: 250 high-quality illustrations depict rare disorders which previously were only described.

Our thanks go to our colleagues at the VU Univer- Preface to the Third Edition sity Medical Center and to those in other hospitals Reading through the prefaces of the two previous edi- who referred their patients to us. We are indebted to tions,we can say that much of what was said there still all colleagues who allowed us to use their MR images, holds. At the same time,however,much has changed. published or unpublished,making it possible for us to There has been immense progress in the technical present illustrations of nearly all known white matter possibilities of magnetic resonance and in the know- disorders. Two colleagues were particularly helpful ledge of genetic defects, biochemical abnormalities, and provided us with essential and unpublished f- and cellular processes underlying myelin disorders. ures: our friends Susan Blaser,from the Hospital for This immense progress has prompted us to embark Sick Children in Toronto,and Zoltán Patay,from the upon the enormous task of rewriting the previous King Faisal Hospital in Riyadh. edition and adding 40 chapters. In doing so we have Many people at the VU University Medical Center tried to cover most white matter disorders,hereditary have been of great technical help to us in producing and acquired,and to present a collection of images to high quality images and in providing secretarial illustrate the field to the fullest possible extent. This assistance. The contributions of these people are edition will therefore be more complete than the pre- mentioned separately in the acknowledgements.

This is the second, completely rewritten edition of the widely acclaimed book on MR of myelin, myelination and myelin disorders (1989). In the last five years many new data became available with regard to genetics, molecular biology, the role of cellular substructures on one side and on the other side regarding the growing experience with MR patterns of less common myelin disorders. Not only, therefore, the text has been updated, but many new chapters have been added on disorders of which previously the white matter involvement was less clear. The acquired myelin disorders were reorganized and their backgrounds were more extensively elucidated, to place the MR examinations in the clinical context where they belong.

In June 1987, neurobiologists, immunologists, molecular biologists, virologists and neurologists from several countries met in Vancouver to discuss recent advances of relevance to multiple sclerosis. The symposium was a part of the 22nd Canadian Congress of Neurological Sciences meeting and was sponsored by funds from the Multiple Sclerosis Society of Canada and the Medical Research Council of Canada. The presentations covered five major topics: basic neurobiology, molecular biology, the role of viruses in demyelination, immune function and dysfunction in multiple sclerosis, and clinical magnetic resonance imaging studies. It was heartening to note that scientists from several different disciplines were working towards a common end-point: the understanding and treatment of multiple sclerosis. In this book, speakers at the symposium have each presented a chapter of their findings and discussions. In addition, some non-participants at the symposium have been invited to submit chapters in order to give this volume a more complete scope. It is hoped that the reader will find this book a useful reference for several subjects of interest to multiple sclerosis. In closing, I would like to thank the following for their help and support: the Multiple Sclerosis Society of Canada and the Medical Research Council of Canada for their financial support; the contributors of this book for their manuscripts; Dr. A. Eisen, Mrs. K. Eisen, Mrs. P. Bodnarchuk and Mrs. M. Kim for their efforts in planning and organizing the symposium; and Ms. Catherine Schikowski for her secretarial assistance. Seung U. Kim, M.D. Ph.D.