Abstract
BackgroundNerve damage in diabetic neuropathy (DN) is assumed to begin in the distal legs with a subsequent progression to hands and arms at later stages. In contrast, recent studies have found that lower limb nerve lesions in DN predominate at the proximal sciatic nerve and that, in the upper limb, nerve functions can be impaired at early stages of DN.Materials and MethodsIn this prospective, single-center cross-sectional study, participants underwent diffusion-weighted 3 Tesla magnetic resonance neurography in order to calculate the sciatic nerve’s fractional anisotropy (FA), a surrogate parameter for structural nerve integrity. Results were correlated with clinical and electrophysiological assessments of the lower limb and an examination of hand function derived from the Purdue Pegboard Test.ResultsOverall, 71 patients with diabetes, 11 patients with prediabetes and 25 age-matched control subjects took part in this study. In patients with diabetes, the sciatic nerve’s FA showed positive correlations with tibial and peroneal nerve conduction velocities (r = 0.62; p < 0.001 and r = 0.56; p < 0.001, respectively), and tibial and peroneal nerve compound motor action potentials (r = 0.62; p < 0.001 and r = 0.63; p < 0.001, respectively). Moreover, the sciatic nerve’s FA was correlated with the Pegboard Test results in patients with diabetes (r = 0.52; p < 0.001), prediabetes (r = 0.76; p < 0.001) and in controls (r = 0.79; p = 0.007).ConclusionThis study is the first to show that the sciatic nerve’s FA is a surrogate marker for functional and electrophysiological parameters of both upper and lower limbs in patients with diabetes and prediabetes, suggesting that nerve damage in these patients is not restricted to the level of the symptomatic limbs but rather affects the entire peripheral nervous system.
Highlights
Distal symmetric diabetic polyneuropathy (DN) is one of the most severe complications of diabetes mellitus (Tesfaye et al, 2005; Feldman et al, 2017)
All values are shown as mean ± standard deviation. n.a, not applicable; NDS, Neuropathy Disability Score; neuropathy symptom score (NSS), Neuropathy Severity Score; FA, fractional anisotropy; HbA1c, glycated hemoglobin; GFR, glomerular filtration rate; HDL, high density lipoprotein; LDL, low density lipoprotein; NCV, nerve conduction velocity; m/s, meters per second; SNAP, sensory nerve action potential; compound muscle action potential (CMAP), compound motor action potential; μV, microvolt
Except for the Pegboard test of both hands in the men subgroup, all Pegboard parameters were significantly correlated with FA in the diabetes group
Summary
Distal symmetric diabetic polyneuropathy (DN) is one of the most severe complications of diabetes mellitus (Tesfaye et al, 2005; Feldman et al, 2017). Despite the assumption that length-dependent nerve damage in DN starts at the level of the feet and progresses to further proximally with an involvement of the upper limbs at later stages, recent studies revealed that sensory and motor functions of the upper limb are frequently affected already at early stages of DN but often remain undiagnosed until a certain degree of functional impairment becomes apparent, indicating that the progression of nerve fiber damage at the level of the hands and arms may parallel the progression of nerve fiber damage at the level of the feet and legs (Kopf et al, 2018a; Yang et al, 2018). Nerve damage in diabetic neuropathy (DN) is assumed to begin in the distal legs with a subsequent progression to hands and arms at later stages. Recent studies have found that lower limb nerve lesions in DN predominate at the proximal sciatic nerve and that, in the upper limb, nerve functions can be impaired at early stages of DN
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