The first signs of diabetic neuropathy typically result from small-diameter nerve fiber dysfunction. This review synthesized the evidence for small-diameter nerve fiber neuropathy measured via quantitative sensory testing (QST) in patients with diabetes with and without painful and non-painful neuropathies. Electronic databases were searched to identify studies in patients with diabetes with at least one QST measure reflecting small-diameter nerve fiber function (thermal or electrical pain detection threshold, contact heat-evoked potentials, temporal summation or conditioned pain modulation). Four groups were compared: patients with diabetes (1) without neuropathy, (2) with non-painful diabetic neuropathy, (3) with painful diabetic neuropathy and (4) healthy individuals. Recommended methods were used for article identification, selection, risk of bias assessment, data extraction and analysis. For the meta-analyses, data were pooled using random-effect models. Twenty-seven studies with 2422 participants met selection criteria; 18 studies were included in the meta-analysis. Patients with diabetes without symptoms of neuropathy already showed loss of nerve function for heat (standardized mean difference (SMD): 0.52, p<0.001), cold (SMD: -0.71, p=0.01) and electrical pain thresholds (SMD: 1.26, p=0.01). Patients with non-painful neuropathy had greater loss of function in heat pain threshold (SMD: 0.75, p=0.01) and electrical stimuli (SMD: 0.55, p=0.03) compared with patients with diabetes without neuropathy. Patients with painful diabetic neuropathy exhibited a greater loss of function in heat pain threshold (SMD: 0.55, p=0.005) compared with patients with non-painful diabetic neuropathy. Small-diameter nerve fiber function deteriorates progressively in patients with diabetes. Because the dysfunction is already present before symptoms occur, early detection is possible, which may assist in prevention and effective management of diabetic neuropathy.

https://drc.bmj.com/content/bmjdrc/8/1/e001566.full.pdf

Altered pain processing in patients with type 1 and 2 diabetes: systematic review and meta-analysis of pain detection thresholds and pain modulation mechanisms

Small fiber neuropathy (SFN) is a kind of peripheral neuropathy in which the thinly myelinated A δ fibers and unmyelinated C fibers are predominantly affected, characterized by allodynia, analgesia, thermoanesthesia and/or autonomic nerve dysfunction. Nerve conduction velocity (NCV) detection can detect the pathological changes of large fibers (Aα and Aβ fibers) but not of small fibers, which lack of value in the diagnosis of SFN. Progress of the examinational and diagnostic methods for the neuropathological, neuroelectrophysiological and autonomic nerve functions of SFN in recent years were introduced in this paper. DOI: 10.3969/j.issn.1672-6731.2017.11.013

Research progress of the diagnosis of small fiber neuropathy

OBJECTIVE: To evaluate the small fiber function in patients with type 2 diabetes mellitus of the early stage by measuring the sensory threshold with the quantitative temperature testing technology. METHODS: Twenty cases of patients with type 2 diabetes with no neurological deficit (DM group) and twenty age and sex-matched healthy controls underwent the detecting of cold sensory threshold (CST), warm sensory threshold (WST), cold pain threshold (CPT), heat pain threshold (HPT) in both inside of their hands. RESULTS: There was no significant difference in CST, WST, CPT and HPT between left and right inside of hand of the same sample among all the testers. But the four kinds of threshold showed significant difference in the right inside of hand between patients and healthy people ( P < 0.05). In addition, the CST and WST differed significantly in the left inside of hand between the patients and healthy controls while the CPT and HPT showed no significant difference in the left inside of hand between them. Patients group and control group with CST and WST on the left side of the comparison difference was statistically significant (P < 0.05). CONCLUSION: Quantitative analysis of temperature sense threshold can not only reflect increase of the pain threshold value, also can reflect its decrease, i. e. hyperalgesia, which may help to diagnose small fibrous peripheral neuropathy recognition, especially in early diabetic peripheral neuropathy.

Wei Feng

Papers

The significance of quantitative temperature sense thresholds in diagnosis of small fibrous sensory neuropathy in patients with type 2 diabetes