Observing nociceptive detection thresholds and evoked potentials in diabetic patients with and without painful neuropathy

Abstract

Aim: Diabetic polyneuropathy is the most described complication in patients with diabetes mellitus. A significant percentage of these patients experience disabling neuropathic pain (painful diabetic polyneuropathy). Small nerve fibers are primarily responsible for peripheral nociception, but objectively assessing its function is challenging. The primary objective of this study was to explore the task execution and outcomes of intra-epidermal electrical stimulation technique that combines nociceptive detection thresholds (NDT) and evoked potentials (EPs) in patients with diabetes. We compared the results of diabetic patients, both with and without painful diabetic polyneuropathy, with those of healthy controls to explore potential clinically relevant information. Methods: The NDT-EP method was applied to 38 patients with diabetes (18 with and 20 without chronic painful neuropathy) and 38 age- and sex-matched healthy controls. Individual mean NDTs, psychometric slopes, EP amplitudes, and the effect of the stimuli on EP amplitudes were analyzed and compared between groups using linear regression. Results: The findings revealed significantly lower detection rates, higher NDTs, and lower psychometric slopes in patients with painful diabetic polyneuropathy than in healthy controls. Both patient groups significantly exhibited lower mean EP amplitudes than healthy controls, which were not linked to pulse amplitudes but influenced by stimulus detection. Conclusions: This study showed altered NDT-EP outcomes in patients with painful diabetic polyneuropathy. Whereas the task execution, NDTs, and psychometric slopes may provide valuable insights into small fiber dysfunction, pulse amplitudes seemed not differently encoded in neurophysiological responses to intra-epidermal electrical stimulation near the detection threshold compared to controls. Future studies should investigate whether the altered NDT-EP outcomes could quantify small fiber dysfunction in patients with diabetes mellitus. We recommend further exploration of NDT-EP measures in other patient groups with nociceptive dysfunction.