Preface

 Polyneuropathy is a distinct term for a generalized and relatively homogenous process that affects many peripheral nerves, but it is the distal nerves that are generally more affected by the disorder at large. It also commonly encompasses any disturbance of the peripheral nervous system, including radiculopathies and mononeuropathies and/or disorders involving the nerves of the central and peripheral nervous system. In daily practice, the wide variety of causes must be identified in obtaining a diagnosis and polyneuropathies should be differentiated from other diseases of the peripheral nervous system, including mononeuropathies and multiplex mononeuropathy (multifocal neuropathy) and some disorders of the central nervous system. Central nervous system diseases such as brain tumor, stroke, or spinal cord injury occasionally present symptoms that are difficult to distinguish from polyneuropathies.

The complex structure and function of nerves of the nervous system make them susceptible to a variety of inflammatory, hereditary, infectious, toxicity, and other factors that can impair their health and function, leading to the clinical disorder of polyneuropathy. Although there is a lack of population-based studies, researchers generally agree that no specific cause is identified in up to half of cases of patients with polyneuropathy at referral centers despite deeper investigations.

There are no simple rules one can apply to reliably distinguish the type of polyneuropathy produced by various disease categories (e.g., demyelinating versus axonal, chronic versus acute, and sensory versus motor). The interest in more reliable instruments to apply to diseases involving nerves of the nervous system has become a significant part of the full investigation to clarify the etiologic diagnosis of polyneuropathy. Regarding its management, although several procedures involving conservative and surgical interventions are available, promising biological strategies are needed to open new horizons so the drawbacks of these challenging conditions may be overcome.

 Knowledge about polyneuropathy has advanced on all fronts, significantly, through education and inspirational leadership. Contributors to this first edition of *Demystifying Polyneuropathy - Recent Advances and New Directions* are many of these leaders, and their writing and creativity are remarkable. The authors are practitioners and researchers with an inestimable amount of experience, and they share their knowledge and wisdom, seeking not only to teach but also to inspire those who will follow them. They point out not only what we already know but also what we need to discover, thereby directing a path toward observation, service, and experimentation, each of which is integral to the study of polyneuropathy in imminent and future directions.

As editor, and on behalf of the authors and assistants, I extend my gratitude to the publisher for striking visual content to help create a comprehensive book, complete with unique topic selections, so that the blend of academic and other content is at once logical and stimulating. At this point, I am enormously grateful to the extraordinary team at IntechOpen, including Edi Lipović, Mirena Calmić, and

Maja Božičević. My publishing editorship family always sets the bar high, patiently helping me by leaps and bounds to achieve a finished book. And, definitely, my academic family has embraced this exciting experience while my own little family graciously has allowed me the time to pursue this lovely undertaking.

Finally, I am excited to introduce you, the reader, to our endeavor, shared in three main sections, five chapters in total. In the first section, general considerations and diagnostic approach are discussed through the chapter, The Cutaneous Biopsy for the Diagnosis for the Peripheral Neuropathies: Meissner's Corpuscles and Merkel's, which highlight skin biopsy as an alternative method of peripheral nerve biopsy for the analysis of nerve involvement in the differential of polyneuropathy. Given the relative simplicity of the technique and its ability to provide quantitative data, the test is also likely to be useful in following disease progression or response to treatment. The chapter provides us a comprehensive rationale concerning this method within neuropathies and an update of the available information in this topic.

 In the second section, Etiologies and Pathogenesis, three chapters are included: the first is on HIV-associated neuropathy: the clinical picture of what is triggered by HIV infection and other maladies is very similar; it includes neuropathic pain, tingling sensation, and numbness. Several related aspects are discussed. The second chapter explains how peripheral neuropathy in connective tissue diseases is characterized by different organ disorders due to the loss of immune system tolerance to autoantigens. Peripheral neuropathy is one of the features of these diseases with variable, and it is often seen in the course of the disease. The chapter reviews the clinical, diagnostic, and therapeutic features associated with the common diffuse connective tissue diseases, and it presents future directions. A third innovative chapter is presented about a new definition of a nonclassified polyneuropathy condition called 'working hand syndrome.'

In the third section, Management and New Clinical Applications, a final chapter discusses platelet-rich plasma for injured peripheral nerves. Although polyneuropathy is among the most challenging categories of neurological diseases, effective forms of treatment for polyneuropathy have been introduced over the last decades. Biological therapies are promising using conservative and surgical approaches. Effects mechanisms, clinical guidelines, protocols, and results from bench to bedside are fully described.

We wish to thank those who contributed to these new insights into polyneuropathy. Particularly, we acknowledge our contributing authors for their excellent submissions to this book, and our patients, families, friends, and collaborators for their help and patience at each step in the production of this book. In summary, we hope you enjoy this wonderful reading, and we are proud to have you join us in this unique and new experience.

> **Patricia Bozzetto Ambrosi**  Paris Diderot University, France

Section 1
