Peripheral neuropathy is dysfunction of one or more peripheral nerves (the part of a nerve distal to the root and plexus). It includes numerous syndromes characterized by varying degrees of sensory disturbances, pain, muscle weakness and atrophy, diminished deep tendon reflexes, and vasomotor symptoms, alone or in any combination. Initial classification is based on history and physical examination. Electromyography and nerve conduction studies (electrodiagnostic testing) help localize the lesion and determine whether the pathophysiology is primarily axonal (often metabolic) or demyelinating (often autoimmune). Treatment is aimed mainly at the cause.