Association of Small Fiber Function with Microvascular Perfusion of Peripheral Nerves in Patients with Type 2 Diabetes Study using Quantitative Sensory Testing and Magnetic Resonance Neurography

Introduction/aimsDiabetic small fiber neuropathy (SFN) is caused by damage to thinly myelinated A-fibers (& delta;) and unmyelinated C-fibers. This study aimed to assess associations between quantitative sensory testing (QST) and parameters of peripheral nerve perfusion obtained from dynamic contrast enhanced (DCE) magnetic resonance neurography (MRN) in type 2 diabetes patients with and without SFN.MethodsA total of 18 patients with type 2 diabetes (T2D, 8 with SFN, 10 without SFN) and 10 healthy controls (HC) took part in this cross-sectional single-center study and underwent QST of the right leg and DCE-MRN of the right thigh with subsequent calculation of the sciatic nerve constant of capillary permeability (K-trans), extravascular extracellular volume fraction (V-e), and plasma volume fraction (V-p).ResultsThe K-trans (HC 0.031 min(-1) & PLUSMN; 0.009, T2D 0.043 min(-1) & PLUSMN; 0.015; p = 0.033) and V-e (HC 1.2% & PLUSMN; 1.5, T2D: 4.1% & PLUSMN; 5.1; p = 0.027) were lower in T2D patients compared to controls. In T2D patients, compound z-scores of thermal and mechanical detection correlated with K-trans (r = 0.73; p = 0.001, and r = 0.57; p = 0.018, respectively) and V-e (r = 0.67; p = 0.002, and r = 0.69; p = 0.003, respectively). Compound z-scores of thermal pain and V-p (r = -0.57; p = 0.015) correlated negatively.DiscussionThe findings suggest that parameters of peripheral nerve microcirculation are related to different symptoms in SFN: A reduced capillary permeability may result in a loss of function related to insufficient nutritional supply, whereas increased capillary permeability may be accompanied by painful symptoms related to a gain of function.