Diabetic small fiber neuropathy: clinical and electrophysiological study

Abstract Background Diabetic neuropathy is diagnosed late due to lack of easy and readily available biomarkers; early identification can prompt proper interventions before the irreversible large fiber damage. The aim of this study is to assess small fiber dysfunction using cutaneous silent period (CSP) and sympathetic skin response (SSR) tests in patients with diabetic small fiber neuropathy (SFN) and compare results with clinical, neuropathy severity and quality of life measures. A total of 45 subjects were classified into: Group I: diabetic patients with pure SFN, group II: diabetic patients with mixed fiber neuropathy, and group III: healthy subjects. All underwent evaluation by anthropometric, clinical and quality of life measures, electrophysiological evaluation by CSP and SSR and distal leg skin biopsy. Results Age and gender distribution did not significantly differ between the studied groups. Both patients’ groups showed comparable poor quality of life in relation to healthy subjects. CSP onset latencies and SSR amplitudes significantly correlated with studied clinical and severity measures, but neither correlate with each other in diabetic pure SFN patients. Both CSP and SSR measures were specific in diagnosing diabetic pure SFN, but mostly with poor sensitivity. Combining sensitivities of different CSP and SSR measures improved the overall sensitivity to early screen for SFN in diabetic patients. Conclusions Both CSP and SSR may have the potential to early detect diabetic pure SFN. Suspected diabetic patients with SFN should be separately screened for both somatosensory and sudomotor/autonomic affection.