The First Electrophysiological Abnormality in New-onset DM: Autonomic Tests

Conventional nerve conduction studies (NCS) are used in the electrodiagnosis of diabetic neuropathy. The aim of our study was to investigate diabetic small fiber neuropathy in newly diagnosed type 2 diabetes mellitus (DM) patient group by using autonomic tests.

Our study was conducted on 49 patients (24 female, 25 male) who were newly diagnosed with type 2 DM in the last 3 months and a control group of 25 volunteers. In addition to conventional NCS, sympathetic skin response (SSR) and RR interval variability (RRIV) tests were performed.

The mean upper limb SSR latency of the patient group was more prolonged than that of the control group, whereas the mean lower limb SSR amplitude of the patient group was lower than that of the control group (p=0.002, p<0.001; respectively). The mean resting (R) and deep inspiration (D) RRIV values of the patient group were lower than that of the control group (p=0.037, p<0.001; respectively). In the patient group, the mean R-RRIV and D-RRIV values were found to be positively correlated with the lower limb SSR amplitude (r=0.006, r=0.011; respectively). The mean R-RRIV and D-RRIV change rate of the patient group (D-R)/R was found to be lower than that of the control group (p=0.002).

In our study, we showed that autonomic function tests were impaired in newly diagnosed type 2 DM patients who were found not to have diabetic polyneuropathy by standard electrophysiological study. These findings suggest that standard electrophysiological tests are not sufficient in the early stages of the disease.