Effect of aging on vagus somatosensory evoked potentials and ultrasonographic parameters of the vagus nerve.

Vagus somatosensory evoked potentials (VSEP) and ultrasonography can be used to detect functional and structural changes of the vagus nerve (VN) that are hypothesized to be associated with neurodegenerative diseases. However, it has not yet been established whether age-related changes in the VN occur in the healthy population. In this pilot study we included healthy volunteers in the 26-30 and 51-55 age range who comprised the younger (n = 20) and older (n = 20) groups, respectively. VSEP were recorded separately for stimulation of the auricular branch of the left and right VN. The VN CSA was measured in the transverse plane proximal to the carotid bifurcation, at the level of the distal end of the common carotid artery. No differences were found between the younger and older groups when comparing the average VN CSA (2.01 ± 0.20 vs 2.05 ± 0.20, mm2; p = 0.570) or the CSA of the right (2.08 ± 0.19 vs 2.17 ± 0.24, mm2; p = 0.233) or left VN (1.94 ± 0.26 vs 1.93 ± 0.24, mm2; p = 0.911). The right VN was larger than the left in 95% (n = 19) of older participants and in 65% (n = 13) of younger participants (p = 0.055). In comparison with the younger group, older participants showed significantly longer VSEP latencies of all wave components for electrodes C4-F4 and Fz-F3, of P1 for electrodes C3-F3 and of N1 and P2 for electrodes Fz-F4. The results of this study indicate that older age is associated with longer VSEP latencies but not with changes in VN CSA.