Evoked potentials in diabetes mellitus.

Abnormalities of central afferent and efferent pathways have been revealed by evoked potential studies in diabetic patients. Central conduction time is only slightly prolonged; in afferent pathways the primary sensory neuron is more affected than in the subsequent stages, probably as an expression of a central-peripheral distal axonopathy. Central nervous system abnormalities are more frequent in patients with peripheral neuropathy, but evoked potential can be abnormal even in patients without neuropathy. Brainstem auditory evoked potential (BAEP), somatosensory evoked potentials (SEPs) and visual evoked potentials (VEPs) can be affected together, but isolated abnormalities are more frequently observed. Diffuse neuropathological changes have been found in the optic nerves, periventricular regions, brainstem and spinal cord in postmortem pathological studies. Similar changes have been found in animals with experimental diabetes. The pathophysiology of central nervous system (CNS) abnormalities is uncertain, many causes are probably active in including neural damage: chronic hyperglycemia, hypoglycemic episodes, angiopathy, blood-brain barrier dysfunction and others, still unknown.