In this book the author presents new nosological perspectives of early Guillain-Barré syndrome starting from his clinical, electrophysiological, pathological and imaging studies. Detailed autopsy studies have demonstrated the relevance of lesions in proximal nerve trunks, and particularly in spinal nerves. Nerve ultrasonography has shown that the most frequent changes, consisting of increased cross-sectional area and loss of physiologic hyperechoic boundaries, are localized in spinal nerves. Muscle MRI seems very useful to delimitate the topography of denervation and to assess its evolution over the clinical course.