Does electrophysiology and treatment response differ in idiopathic vs diabetic chronic inflammatory demyelinating polyneuropathy (CIDP)?

Introduction: Sensory electrophysiology and Terminal latency index (TLI) differences have been described in various CIDP sub-groups. Objective: Evaluate electrophysiology, TLI and treatment response in idiopathic and diabetic CIDP. Methods: Retrospective review of 147 patients with CIDP who underwent electrodiagnostic evaluation (January 2000-December 2015). 89 patients fulfilled electrophysiological criteria described by Ad hoc subcommittee of American Academy of Neurology (AAN) and Albers et al. We excluded patients (31) with acute inflammatory demyelinating neuropathy, hereditary sensorimotor neuropathy, vasculitis and polyneuropathy with paraproteinemia. 58 patients were divided into idiopathic (40) and diabetic (18) groups. These groups were compared for age, sex, history of cancer, CSF protein, response to treatment, sensory response abnormalities and TLI measurements using chi-square tests for binary and categorical variables and t-tests for continuous measures. All testing was at the alpha=0.05 level. Results: Group differences for age, sex, history of cancer, CSF protein and treatment response were not significant. Comparing TLI values in measurable responses, the difference between the two groups for tibial TLI was significant (p=0.012), with idiopathic group having a lowermean as compared to the diabetic. TLI values differences formedian, ulnar and peroneal nerves were not significant. The difference in abnormal rates of sensory responses was significant for the sural nerve with the idiopathic group having a lower rate compared to the diabetic group (80% vs 100%, p\u3c0.05). No differences were noted for the ulnar, median and radial nerves. Conclusion: Tibial TLI and sural sensory responses have some value in differentiating the two groups. Larger prospective studies are needed to confirm our findings