Which Occurs First in Patients with Type 2 Diabetes Mellitus? Central or Peripheral Neuropathy

ABSTRACT

Objective: To study the central and peripheral neuropathy by electrophysiological tests in type two diabetes mellitus patients (DM-2) before symptomatic peripheral neuropathy. Methodology: DM-2 (n=30) and age- and sex-matched (n=30) healthy subjects (controls) with normal bilateral sural sensory nerve action potentials (SNAPs) were selected after informed written consent. Their 16-channel EEG records were transformed using Fast Fourier Transformation (FFT). EEG power spectra obtained were log-transformed and compared using student’s t-test. Results: DM-2 without symptoms of peripheral neuropathy had low amplitudes of bilateral sural SNAPs in comparison to the controls though they were above the normal cut-off values of ≥ 4 μV. In EEG, DM-2 had more beta power (p<0.05) at midline Fz (24.77±11.58 vs. 12.26±11.55,), Cz (33.04±19.41 vs. 17.65±19.51,), and Pz (30.34±16.54 vs. 16.13±15.57,) and at other sites (Fp2, F8, F4, C4, T4, T6, P4, O2, Fp1, F7, F3, C3, T3, T5, P3, and O1) during eyes-close condition. Similar differences in beta power were seen in eyes-open condition. The delta power was more (p<0.05) in DM-2 during eyes-close condition at midline Fz (64.64±34.54 vs. 47.37±22.47), Cz (73.87±45.07 vs. 51.73±25.58), and Pz (66.13±36.84 vs. 44.15±19.68) and at other sites (Fp2, F8, C4, P4, O2, Fp1, F7, T3, T5, O1). Similar differences in delta power were seen in eyes-open condition. Alpha activities were more (p<0.05) in DM-2 at some sites during eyes-open condition. Conclusion: Diffuse central neuropathy occurs along with the peripheral neuropathy in DM-2 as measured by the electrophysiological tests.