The most prevalent microvascular complication of diabetes mellitus is neuropathy, which encompasses distal symmetric polyneuropathy, mononeuropathy, radiculoplexopathy, and autonomic neuropathy. Intensive glucose control prevents and effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus. However, the effect of strict glucose control itself is at modest in those with type 2 diabetes. Although we have better understanding of the mechanism of diabetic neuropathy, many pharmacologic trials for the targeting underlying nerve damage have reported unsuccessful results. In this review, the effects and limitations of the current therapeutic options will be discussed.

Diabetic polyneuropathy (DPN) causes neuropathic pain with reduced quality of life as well as diabetic foot ulceration which sometimes resulted in amputation. Early detection and improved knowledge of pathogenic pathways are important to prevent and to manage DPN. The screening methods and several tests to diagnose DPN-quantitative sensory testing, skin biopsy, corneal confocal microscopy, etc.-will be described.

This article provides an overview for understanding the classification and pathogenesis of diabetic neuropathy. Diabetic neuropathies are prevalent disorder. The most common manifestation is distal symmetric polyneuropathy, but various patterns of neuropathy can occur. New information for the pathogenesis of diabetic neuropathy continues to emerge, which will lead to identifying new drug targets.

Although various criteria on the diagnosis of diabetic neuropathy are applied from trial to trial, being tailored in concert with its purpose, the utmost evidences of the diagnosis are subjective symptoms and objective signs of neurologic deficit. The application and interpretation of auxiliary electrophysiological test including nerve conduction study (NCS) should be made on the context of clinical pictures. The evaluation of the functions of small, thinly myelinated or unmyelinated nerve fibers has been increasingly stressed recently with the advent of newer techniques, e.g., measurement of intraepidermal fiber density, quantitative sensory testing, and autonomic function test. And the studies with those techniques have shed light to the nature of the evolution of diabetic neuropathy. The practical application of these techniques to the diagnosis of diabetic neuropathy in the individual patients, however, should be made cautiously due to several shortcomings: limited accessibility, wide overlapping zone between norm and abnormality with resultant unsatisfactory sensitivity and specificity, difficulty in performing subsequent tests, unproven quantitative correlation with clinical deficit, and invasiveness of some technique. NCS, as an extension of clinical examination, is still the most reliable electrophysiological test in evaluating neuropathy and gives the invaluable information about the nature of neuropathy, whereas the newer techniques need more refinement of the procedure and interpretation, and the accumulation of large scaled data of application to be considered as established diagnostic tools of peripheral neuropathy.