Influence of diabetes mellitus on chronic inflammatory demyelinating polyneuropathy

Patients with diabetes occasionally develop clinical and electrodiagnostic features suggestive of chronic inflammatory demyelinating polyneuropathy (CIDP). To clarify the role of diabetes in patients with a CIDP-like syndrome, we compared the clinical, pathological, and electrodiagnostic features of 14 patients (10 men, 4 women) with diabetes and CIDP (DM-CIDP) to 60 patients with idiopathic CIDP (I-CIDP). The average duration of diabetes was 9 years. The patients with DM-CIDP were older and more often complained of imbalance compared to the idiopathic group, but the frequency of other symptoms and neurologic findings were similar. The mean amplitude of the ulnar compound muscle action potential in the DM-CIDP group was comparatively reduced, the sural sensory nerve action potential was more often absent, and axonal loss was more commonly observed on nerve biopsy. The response rate to treatment was similar, but the magnitude of functional recovery was greater in patients with I-CIDP. Thus, our patients with diabetes and CIDP had clinical features similar to those with idiopathic CIDP, but their nerve conduction studies and nerve biopsies showed more severe axonal loss and the degree of improvement following treatment was less favorable. These differences most likely reflect the additive effects of superimposed diabetic axonal polyneuropathy in patients who develop CIDP.