Peripheral Neuropathies

Disorders affecting the peripheral nerves are a common neurological problem. Peripheral neuropathies can be primary entities or a manifestation of several systemic illnesses, including diabetes, infections, vasculitis, neoplastic disorders, and vitamin deficiencies, or the consequence of toxins. In as many as 30% of patients the mechanism responsible for the peripheral neuropathy remains elusive. From a biological standpoint, peripheral neuropathies are the clinical manifestation of dysfunction of peripheral axons and/or the Schwann cells that ensheathe them. Therefore, research in peripheral neuropathies has focused on understanding how peripheral axons (motor, sensory, and autonomic) develop and are maintained, and how and why Schwann cells myelinate these axons. This chapter reviews the basic morphology and physiology of peripheral nerves, focusing on the peripheral axon and the myelin sheath, and describes the main conditions affecting these structures.