Age effect on far field potentials from the brain stem after transcutaneous vagus nerve stimulation.

Recently, a new electrophysiological method for the assessment of vagus nerve function in the brainstem has been proposed in healthy participants. Before this procedure may be applied to patients with neurodegenerative diseases, its feasibility in elderly healthy participants and a possible age effect on the measurement have to be investigated. The vagus sensory evoked potentials (VSEP) after transcutaneous electric stimulation of the sensory auricular branch of the vagus nerve have been assessed in healthy younger and elderly participants. VSEP measured as far field potentials probably originating in vagus nuclei in the brainstem were recorded in 20 of 22 younger as well as in 39 of 43 elderly healthy participants. Latencies were significantly longer in the elderly as compared to the younger participants, while no clear age effects on amplitudes were identified. These results indicate that the assessment of VSEP is feasible also in elderly healthy participants. This is a prerequisite for testing this method in elderly patients with neurodegenerative diseases like Alzheimer and Parkinson disease as a noninvasive tool to detect an affection of the brainstem nuclei of the vagus nerve early in their course.