Book excerpt: "This book is aimed at describing clinical features of various kinds of involuntary movements by demonstrating a number of cases on video. All cases presented in this book were directly observed and studied by at least one of the five authors. We will also discuss the current consensus about the classification, pathophysiology and current treatment of each involuntary movement. This book adopts a unique way of looking at movement disorders; that is considering two aspects of the diagnosis, axis 1, the phenomenology and, axis 2, the etiology and/or pathophysiology. The visual appearance (video) is a big part of axis 1"--