P1-4-01. Evaluation of small fiber involvement using pain-related evoked potentials in patients with type 1 and type 2 diabetes

The pathophysiology of diabetic neuropathy presumably differs between type1 and type 2 diabetes mellitus (T1DM and T2DM), and neuropathic pain is more frequent in patients with T2DM than T1DM. To investigate difference in small fiber involvement, we studied painrelated evoked potentials (PREPs) using intraepidermal electrical stimulation (IES) selective to A-delta-fibers and C-fibers in patients with T1DM (n = 20) and T2DM (n = 20). IES was applied in the back of hand and foot, and PREPs were recorded from the Cz electrode referenced to the linked earlobes. We evaluated the thresholds, and PREP latencies and amplitudes. Nerve conduction studies were performed in the ipsilateral limbs. There were no significant differences in age and hemoglobin A1c levels between the groups, but disease duration was significantly longer in T1DM. In nerve conduction study, patients with T1DM showed significantly more severe large fiber dysfunction in the lower extremity, however less pain/paresthesia than T2DM patients. PREPs study showed no significant differences in all the parameters between T1DM and T2DM. Diabetic neuropathy in T1DM showed relatively mild small fiber involvement compared with large fiber dysfunction, and this characteristic pattern might be related to the difference in the pathophysiology or neuropathic symptoms.