Impaired function of C-nociceptors in chronic inflammatory demyelinating polyradiculopathy indicated by electrically induced axon flare reflex

INTRODUCTION:In chronic inflammatory demyelinating polyradiculopathy (CIDP) the impairment of unmyelinated nerve fibers appears unexpected. The measurement of the electrically induced axon flare reflex is a clinical test to assess the peripheral C-nociceptor function. In this study we compared the flare area in patients suffering from chronic inflammatory demyelinating polyradiculopathy with healthy subjects. MATERIALS AND METHODS:We examined 18 patients fulfilling the criteria for CIDP (11 male, mean age 51.8 years, SD 15.1) and 18 age-matched adult healthy volunteers (control group) (11 male, mean age 51.9 years, SD 15.8). The flare responses were elicited by transcutaneous electrical stimulation and recorded by laser Doppler imaging. RESULTS:There was a significant reduction of electrically induced maximum flare area in the foot dorsum of CIDP patients (t-value 2.08, p=0.04) which proved to be length-dependent measured by a numerical index comparing the results with the forearm and thigh. The repeated measures ANOVA revealed statistically significant smaller flare areas in all body regions for the CIDP group (p