LAUSR

We reported an electrophysiological severity classification for diabetic polyneuropathy (DPN) using a nerve conduction study (NCS). This new classification system combines of the amplitude and velocity of NCS and classifies DPN into five stages. Stage 0 is the mildest stage, while Stage IV is the most severe. Here, we clarified the association of this classification system with small fiber abnormalities. We measured intra-epidermal nerve fiber densities (IENFD) and pain threshold using intra-epidermal electrical stimulation (IES) to evaluate the function of small fibers. We recruited 65 patients with diabetes, and performed NCS, skin biopsy and pain threshold using IES. The mean IENFD observed in the skin biopsies were 8.27 n/mm in Stage 0, 7.79 n/mm in Stage I, 4.49 n/mm in Stage II, 2.85 n/mm in Stage III, and 0 n/mm in Stage IV. The mean pain thresholds were 0.05 mA in Stage 0, 0.11 mA in Stage I, 0.08 mA in Stage II, 0.27 mA in Stage III, and 0.59 mA in Stage IV. In summary, the abnormalities of IENFD and pain threshold correlated with electrophysiological severity. The present results indicate that the large fiber dysfunction in DPN progresses in parallel with the small fiber abnormalities.