Gender Differences in Neuroselective Current Perception Thresholds of the Trigeminal and Median Nerves

Abstract

Purpose : The goal of this study was to ascertain gender differences in sensory thresholds by measuring current perception threshold (CPT) values of the trigeminal and median nerves in healthy individuals.Materials and Methods : CPT values were measured using a Neurometer® (Neurotoron, Baltimore, MD, USA) when electrical stimulation of 2, 000, 250, or 5 Hz was applied to the left preauricular (trigeminal nerve) and thenar eminence (median nerve) regions in 20 healthy volunteers (10 males and 10 females with a mean age of 24.4 years). The day-to-day reliability of CPT was first verified in the trigeminal region by a test-retest method using an interclass correlation coefficient (ICC). The CPT values were then measured and statistically analyzed to evaluate whether the values were influenced by the electrical stimulation frequency and gender difference.Results : Irrespective of the stimulation frequency, the ICC values were high (2, 000 Hz : 0.62, 250 Hz : 0.80, 5 Hz : 0.86), showing the high day-to-day reliability of CPT. The electrical frequency of the stimulation significantly influenced the CPT (ANOVA : p<0.0001) ; the mean CPT value during 2, 000 Hz stimulation was significantly higher than the value during 250 and 5 Hz stimulation (Bonferroni test : p<0.001). For median nerve stimulation, the mean CPT was lower for women than for men, but no significant gender difference was identified (ANOVA : p=0.11). Conversely, gender exerted significant effects on CPTs (ANOVA : p=0.02) for trigeminal nerve simulation. As to stimulation frequency, the mean CPT following 2, 000 Hz stimulation of the trigeminal nerve was significantly lower for women than for men (Bonferroni test : p<0.001).Conclusion : The results suggest that healthy women are more sensitive to tactile or pressure sensations compared to healthy men, and that the effects of gender differences on the sensory threshold can be ignored with pain-related nerve fibers such as Aδ and C fibers.