Retrospective study of the ultrasound characteristics of the tibial nerve in patients with type 2 diabetic peripheral neuropathy.

Background: Ultrasound is a promising imaging examination for type 2 diabetic peripheral neuropathy (DPN). This study aimed to explore the risk factors of ultrasound diagnostic characteristics in the tibial nerves of patients with type 2 DPN.

Methods: The Michigan Neuropathy Screening Instrument (MNSI) was used for neuropathy evaluation, and 520 patients with type 2 diabetes were divided into a DPN group and non-DPN (NDPN) group with 2 points as the cut-off value. The two groups were matched at a ratio of 1:1 according to age, BMI, calf circumference, and gender, resulting in 44 matched pairs. The dependent variable was type 2 DPN and the concomitant variables were the width, thickness, cross-sectional area, and unclear honeycomb-like structure of the tibial nerve. A 1:1 matched conditional logistic regression model was established to analyze which ultrasound diagnostic characteristics of the tibial nerve were risk factors for type 2 DPN.

Results: The thickness (OR =5.176, P=0.043) and cross-sectional area (OR =1.659, P=0.030) of the tibial nerve were risk factors for the diagnosis of DPN, while the width and unclear honeycomb-like structure of the nerve were not (P>0.05). In the diagnosis of DPN, the area under the receiver operating characteristic (ROC) curve of the cross-sectional area of the tibial nerve was 0.747, and the sensitivity, specificity, positive predictive value, and negative predictive value were 61.36%, 95.45%, 93.10%, and 71.20%, respectively. The area under the ROC curve of tibial nerve thickness was 0.867, and the sensitivity, specificity, positive predictive value, and negative predictive value were 81.82%, 90.91%, 90.00%, and 83.30%, respectively. The area under the ROC curve of thickness was larger than that of cross-sectional area of the tibial nerve (z statistic =1.800, P=0.07).

Conclusions: The thickness and cross-sectional area of the tibial nerve measured by ultrasound are risk factors for type 2 DPN. The diagnostic sensitivity of the thickness is higher than the cross-sectional area, while the diagnostic specificity of the cross-sectional area is higher than the thickness.