Subclinical diabetic neuropathy with normal conventional electrophysiological study

Abstract

For early detection and prevention of diabetic neuropathy, it is important to identify subclinical diabetic neuropathy. Routine nerve conduction study often fails to detect early stage of neuropathy. The purpose of this study is to evaluate the clinical usefulness of electrophysiological indexes in detecting early diabetic neuropathy with no objective clinical or electrophysiological abnormalities. Nerve conduction study of upper/lower limbs was investigated in 31 subclinical diabetic neuropathy patients with normal nerve conduction studies(group I), 38 clinical diabetic neuropathy patients with normal nerve conduction studies(group II) and 31 normal controls. Residual latency (RL), terminal latency index (TLI) and modified F ratio (MFR) were calculated and compared among groups. Compared with controls, MFR of lower limbs and TLI of both upper/lower limbs were significantly decreased in both group I and II (p<0.05). RL was increased in both groups, but the difference was not statistically significant. Comparing the indexes between group I and II, there was no significant difference. RL, TLI and MFR, which reflect distal conduction slowing, may be useful indexes to identify subclinical diabetic neuropathy. The results also suggest that electrophysiological changes that are obscured in routine nerve conduction study are present before the clinical manifestation.