The main purpose of this book is to provide the reader with a better understanding of spinal nerve root injuries caused by various pathologies (e.g. disc herniation, space-occupying lesions, trauma etc.). The standard anatomical description of spinal nerve roots origin, course and arrangement (described in the first chapters of the book) is now strongly influenced by the frequent findings of their intraspinal extradural and intradural connecting branches and by other variations, which are considered to be the major cause of the surgical therapy failures. Intraspinal extradural and intradural neuroanatomical roots variations may affect in fact the clinical picture, diagnosis, and surgical treatment; their recognition can minimize the damage to neural structures in the spinal anaesthesia, in spinal operations, in spondylosurgery, in endoscopic surgery, laser discectomy, etc. Their aetiology is unknown and it has to be elucidated, and they are rarely found during the usual preoperational examinations, a reason that encouraged various anatomical dissection studies finalized to their description. The data shown in this book will be surely helpful for traumatologists, orthopaedists, spinal surgeons, neurosurgeons, plastic surgeons and for all those dealing with intraspinal variations of nerve roots.