Electrophysiological status of sural nerves in type 2 diabetes mellitus patients before symptomatic peripheral neuropathy

Abstract

Introduction. Neuropathies in type 2 diabetes mellitus (T2DM) patients are well known. However, electrophysiological changes in their peripheral nerves, particularly before overt peripheral neuropathy have received much less attention. Hence, we aimed to study the electrophysiological status of bilateral sural nerves in T2DM patients who do not show symptoms and signs of peripheral neuropathy. Material and methods. We selected 35 T2DM male patients and 35 age- and sex-matched control subjects without any clinical evidence of peripheral neuropathy and infectious, systemic, metabolic, and neuropsychiatric illnesses after informed written consent. Nerve conduction study (NCS) of bilateral sural nerves of both the groups was done at the lab temperature of 26 ± 2oC by antidromic method of stimulation using standard methods. Their latency, conduction velocity, amplitude, and duration of bilateral sural sensory nerve action potentials (SNAPs) were measured and compared. Results. T2DM patients had reduced amplitudes of bilateral sural SNAPs compared to control subjects [left (12.46 ± 3.77) μV vs. (16.42 ± 4.58) μV, p = 0.000; right (11.96 ± 4.45) μV vs . (16.62 ± 6.20) μV, p = 0.001] though they were above the normal cut-off value of ≥ 4 μV. T2DM patients showed prolonged durations of bilateral sural SNAPs compared to the control subjects [left (1.99 ± 0.38) ms vs . (1.67 ± 0.27) ms, p = 0.000; right (1.92 ± 0.47) ms vs . (1.55 ± 0.33) ms, p = 0.000]. Conclusion. Reduced amplitudes and prolonged durations of bilateral sural SNAPs are the electrophysiological alterations, suggestive of peripheral neuropathy, in T2DM patients that appear before they show clinical symptoms and signs of peripheral neuropathy.