Imaging photoplethysmography for evaluation of cutaneous sensory nerve fiber function

Abstract

Peripheral neuropathy refers to peripheral nervous system dysfunction which affects up to 2% of the world's population. This condition is caused by damage to the small nerve fibers, hence its assessment is still challenging due to the lack of simple, non-invasive and objective diagnostic techniques. The present study aimed to develop and evaluate a simple, objective and non-invasive technique for assessment of small cutaneous sensory nerve fiber function. Our approach is based on utilization of imaging photoplethysmography and local skin heating. The effectiveness of the method was evaluated on young, healthy volunteers (n = 14) after 10 minutes of 45-degree local skin heating, while recording a photoplethysmographic signal simultaneously from the intact (control) and anesthetized skin (topical application of Emla gel) regions. In the anesthetized skin region, the local heating evoked flare area was 44% lower than that of intact skin. A similar trend was observed for the perfusion curve- perfusion peak in the anesthetized skin was substantially reduced in comparison to intact. The results indicate for the potential of the imaging photoplethysmography in the assessment of the small nerve fiber function. It is believed that this technique could be utilized in the clinics in the future to examine neuropathy patients and diagnose neuropathy.