Comparison of diabetes patients with “demyelinating” diabetic sensorimotor polyneuropathy to those diagnosed with CIDP

BACKGROUND We have previously identified a subset of diabetic sensorimotor polyneuropathy (DSP) patients with probable demyelination related to poor glycemic control. We aimed to determine whether the clinical characteristics and electrodiagnostic classification of nerve injury in diabetes patients with "demyelinating" DSP (D-DSP) differed from those diagnosed with chronic inflammatory demyelinating polyneuropathy (CIDP) (CIDP + diabetes mellitus [DM]). METHODS D-DSP (56) and CIDP + DM (67) subjects underwent clinical examination and nerve conduction studies (NCS), and were compared using analysis of variance, contingency tables, and Kruskal-Wallis analyses. RESULTS Of the 123 subjects with a mean age of 60.5 ± 15.6 years and mean hemoglobin A1c (HbA1c) of 8.2 ± 2.2%, 54% had CIDP + DM and 46% had D-DSP. CIDP + DM subjects were older (P = 0.0003), had shorter duration of diabetes (P = 0.005), and more severe neuropathy as indicated by Toronto Clinical Neuropathy Score (TCNS) (P = 0.003), deep tendon reflexes (P = 0.02), and vibration perception thresholds (VPT) (P = 0.01, P = 0.02). The mean HbA1c value for D-DSP subjects (8.9 ± 2.3%) was higher than in CIDP + DM subjects (7.7 ± 2.0%, P = 0.02). CONCLUSIONS The clinical phenotype and electrophysiological profile of CIDP + DM patients is marked by more severe neuropathy and better glycemic control than in patients with D-DSP. These findings indicate that these two conditions - despite similarities in their electrophysiological pattern of demyelination - likely differ in etiology.