Terminal latency index (TLI) and sensory electrophysiology in paraproteinemic chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)

Objective: To differentiate sensory electrophysiology, TLI and treatment response in patients with paraproteinemic CIDP. Background: Low TLI has been reported as a useful electrophysiological marker for MAG-CIDP. To our knowledge comparison of sensory electrophysiology and TLI of paraproteinemic CIDP subgroups have not been previously reported. Design/Methods: Retrospective review (January 2000-December 2015) of 89 patients with CIDP fulfilling electrophysiological criteria (AAN ad hoc subcommittee and Albers and colleagues).CIDP patients with diabetes(n=18) were excluded. 71 patients were divided into idiopathic (n=40) and paraproteinemic CIDP (n=31). Paraproteinemic CIDP subgroups: MAG (8), non-MAG(8) and IgG(15) were compared to idiopathic CIDP (40). These groups were compared for demographics, history of cancer, CSF protein, sensory conductions, TLI measurements and response to treatment using chi-square tests for binary and categorical variables and t-tests for continuous measures. Results: There was a higher proportion of females in idiopathic-CIDP compared to non-MAG-CIDP (50% vs 13%). Idiopathic group having a higher proportion of patients on monotherapy (59% vs 50%) and combination therapy (38% vs 17%) compared to non-MAG. Higher mean CSF protein compared to MAG-CIDP(p=0.001) was seen in the idiopathic. The difference between idiopathic and IgG-CIDP was significant for overall Rx response (p=0.025) and Rx response in patients with follow-up(p=0.01). For both variables, patients in the idiopathic group had a higher proportion of patients on combination therapy and lower proportion of no treatment offered compared to patients in the IgG-CIDP. 50% of non-MAG-CIDP patients had a history of cancer vs 0% of MAG-CIDP. None of the other differences were significant. There were no group differences in sensory electrophysiology and TLI. Conclusions: Sensory electrophysiology and TLI may have no value in differentiating paraproteinemic CIDP. CSF protein is higher in idiopathic CIDP compared to MAG-CIDP. Idiopathic-CIDP has a higher proportion of females compared to non-MAG-CIDP and a higher proportion of patients on combination therapy compared to IgG-CIDP. Cancer screening should be considered in patients with non-MAG-CIDP.