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  • Updated 01.02.2021
  • Released 03.08.1996
  • Expires For CME 01.02.2024

Diabetic neuropathies

Introduction

Overview

Diabetic neuropathies include a variety of disorders that afflict diabetics fairly exclusively and are characterized by variable degrees of peripheral nerve damage. The author emphasizes the diversity of the resulting clinical syndromes. In terms of arresting or reversing the commonest type, chronic diabetic sensory-motor polyneuropathy, unfortunately no progress has been made. Other types of neuropathy in the diabetic, such as proximal diabetic neuropathy, sometimes respond to immunomodulatory and/or anti-inflammatory treatments. Several randomized controlled studies show the efficacy of some of the newer anticonvulsant medications such as pregabalin, or antidepressants, such as duloxetine, in the treatment of diabetic neuropathic pain.

Key points

• Diabetes is the leading cause of peripheral polyneuropathy, and diabetic neuropathy is the most prevalent complication of diabetes, affecting about half of diabetic patients.

• Peripheral nerve dysfunction in diabetics may be caused by other common causes of neuropathies.

• The diagnosis of diabetic polyneuropathy includes a variety of modalities that test more specifically various peripheral nerve fibers including large fiber, small fiber somatic, and small fiber autonomic fibers.

• Although chronic distal sensorimotor polyneuropathy is the most common type of diabetic neuropathy, other generalized and focal acute and chronic diabetic neuropathies are not uncommonly encountered in neurologic clinical practice.

• Optimal glucose control remains the most important prevention and treatment strategies in diabetic polyneuropathy.

Historical note and terminology

Diabetes mellitus has 4 major systemic complications: (1) neuropathy, (2) retinopathy, (3) nephropathy, and (4) vasculopathy. Diabetic neuropathy is defined as the presence of symptoms and signs of peripheral nerve dysfunction in patients with insulin-dependent or noninsulin-dependent diabetes mellitus. In addition, diabetes remains the leading cause of peripheral polyneuropathy in developed countries.

Diabetic neuropathies consist of a variety of syndromes resulting from different types of damage to peripheral or cranial nerves. These complications of diabetes have been recognized for at least 2 centuries. In the late 1800s, a series of papers appeared in which many of the subtypes of diabetic neuropathies were defined (04; 81; 12; 104). Included in these descriptions are patients with diabetic sensorimotor polyneuropathy as well as others with proximal diabetic, truncal, median, and ulnar neuropathies. Bruns focused further on the entity of proximal diabetic neuropathy (24). Diabetic polyneuropathy was recognized as having various manifestations; Leyden identified 3 subtypes: painful, ataxic, and paralytic. Autopsy studies on several patients showed peripheral nerve degeneration (81; 12). In 1922, Kraus proposed a classification of diabetic neuropathies into polyneuropathy and mononeuropathy as well as motor, sensory, and cranial types (75). The contemporary classification of diabetic neuropathies is shown in Table 1 (123; 16; 120).

Table 1. Classification of Diabetic Neuropathies

Generalized neuropathies

• Chronic sensorimotor polyneuropathy
• Autonomic neuropathy
• Small fiber neuropathy
• Hyperglycemic neuropathy
• Acute painful sensory neuropathy
• Treatment-induced neuropathy
• Coexisting chronic inflammatory demyelinating polyneuropathy

Focal and multifocal neuropathies

• Cranial neuropathies
• Truncal neuropathy
• Proximal diabetic neuropathy (diabetic amyotrophy, diabetic radiculoplexopathy)
• Focal limb mononeuropathies

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