Evaluation of Small Fiber Peripheral Neuropathy With Infrared Thermographic Camera in Prediabetes

Introduction: The typical microvascular complications of diabetes may ocasionaly occur in patients with prediabetes (PD). Diabetic peripheral neuropathy (DPN) is associated with poor glycemic control as well as with the metabolic syndrome components independently of HbA1c levels. Small fiber DPN is one of the most chalenging diagnosis due to the usualy normal physical examination as well as electrophysiological nerve evaluation. The thermographic camera has emerged as a novel tool for the detection of small nerve fiber dysfunction. The aim of the present study was to evaluate thermography of the plantar foot in individuals with PD. Methods: This was a cross-sectional study with a sample of 51 patients aged 27 to 71 years. Patients were divided into the following three groups: control (n = 18), diabetic (n = 17), and prediabetic (n = 16). The diagnosis of PD was made according to ADA standards. Thermographic analysis of the plantar region was performed using a FLIR C2 camera. Results: Overall, 510 foot regions were analyzed. There were significant diferences in plantar temperatures between prediabetes vs controls as follows: hallux (L: 25.24 ± 2.02 vs 23.6 ± 1.79 ºC; p=0.009/ R: 25.44 ± 2.05 vs 23.89 ± 1.73 ºC; p=0.01); fifth metatarsal (L: 26.31 ± 1.72 vs 24.88 ± 1.38 °C; p=0.006 /R: 26.12 ± 1.60 vs 24.74 ± 1.41 °C; p= 0.006); and calcaneus (L: 26.46 ± 1.71 vs 24.93 ± 1.41 °C; p=0.005 / R: 26.58 ± 1.85 vs 25.07 ± 1.18 °C; p=0.004). There were no similar results for temperatures in individuals with diabetes comparing with prediabetes: hallux (L:25.24 ± 2.02 vs 25.76 ± 2.30 °C; p=0.24 /R: 25.44 ± 2.05 vs 25.64 ± 1.92 °C; p=0.38); fifth metatarsal (L: 26.31 ± 1.72 vs 26.03 ± 1.27 °C; p=0.3 / R: 26.12 ± 1.60 vs 26.21 ± 1.57 °C; p=0.43); and calcaneus (L26.46 ± 1.71 vs 26.82 ± 1.41 °C; p=0.23 / R: 26.58 ± 1.85 vs 26.99 ± 1.42 °C; p=0.24). Conclusion: We found siginificant abnormalities in temperature of various sites of the plantar region in PD feets suggesting that small fiber damage may occur before the onset of type 2 diabetes.