02-26-2018 | Neuropathy | Figure | Image
Schematic representation of different clinical presentations of diabetic neuropathy
The spectra of clinical neuropathic syndromes described in patients with diabetes mellitus include dysfunction of almost every segment of the somatic peripheral and autonomic nervous systems. Each syndrome can be distinguished by its pathophysiologic, therapeutic, and prognostic features. Initial neurologic evaluation should be directed toward detection of the specific part of the nervous system affected by diabetes. Diabetes may damage small fibers, large fibers, or both. Small nerve-fiber dysfunction usually, but not always, occurs early and often is present before objective signs or electrophysiologic evidence of nerve damage is found. Small nerve-fiber dysfunction is manifested first in the lower limbs by pain and hyperalgesia. Loss of thermal sensitivity follows, with reduced light touch and pinprick sensation. Large-fiber neuropathies may involve sensory or motor nerves or both. The neuropathies are manifested by reduced vibration (often, the first objective evidence of neuropathy) and position sense, weakness, muscle wasting, and depressed tendon reflexes. Most patients with distal sensory polyneuropathy have a mixed variety, with both large and small nerve-fiber involvement. In the case of distal sensory polyneuropathy, a “glove and stocking” distribution of sensory loss is almost universal. Early in the course of the neuropathic process, multifocal sensory loss may also be found. Diabetic peripheral symmetric polyneuropathy is thought to be a dying-back disorder, with prevailing effects on the axons and consequent demyelination. There is an early functional phase in which metabolic abnormalities are responsible for the clinical symptoms and signs. Later structural changes occur in the nerves so that treatment strategies have been developed to arrest or slow the rate of progression. When neuronal cell death occurs, little can be done to induce recovery. Clearly, all attempts at treating neuropathy should be oriented toward the reversible phase of the disorder.