Atypical diabetic neuropathies

Diabetes is one of the most common conditions in the world and is associated with a broad range of adverse effects in multiple organ systems. Roughly half of all patients with diabetes will develop a typical distal, symmetric polyneuropathy, but several other atypical peripheral nerve conditions can also occur. Treatment induced neuropathy of diabetes is an acute and severely painful small fiber neuropathy that occurs in association with a precipitous drop in glycated hemoglobin levels. Radiculoplexus neuropathies include lumbosacral, cervical, and thoracic forms in which pain and weight loss are followed by weakness and sensory loss in the distribution of a single anatomical region. The underlying process is a monophasic inflammatory microvasculitis that does not seem to respond to immunomodulatory therapy. By contrast, monophasic cranial mononeuropathies are caused by non-inflammatory microvascular ischemia and present acutely followed by slow improvement. Patients with diabetes are also at increased risk for compressive neuropathies, particularly of the median, ulnar, and peroneal nerves. Finally, several lines of evidence indicate increased prevalence of chronic inflammatory demyelinating polyneuropathy (CIDP) in patients with diabetes, although definitive diagnosis of CIDP is often challenging in the setting of concurrent diabetes. This review presents in-depth discussions of these atypical diabetic neuropathies.