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From the Neurologische Klinik (Drs. Kirchner, Stefan, and Haslbeck), Institut für Physiologie und experimentelle Pathophysiologie (Dr. Schmelz), Friedrich-Alexander-Universität Erlangen, and Neurologische Klinik (Dr. Birklein), Johannes-Gutenberg Universität Mainz, Germany.
Address correspondence and reprint requests to Annette Kirchner, University of Erlangen-Nuremberg, clinic of neurology, Schwabachanlage 6, D-91054 Erlangen, Germany; e-mail: annette.kirchner{at}neuro.imed.uni-erlangen.de
Objective: To investigate whether vagus nerve stimulation (VNS) reduces pruritus in humans.
Background: Recently, it has been shown that VNS has antinociceptive and antidepressant effects in humans.
Methods: Eleven patients were investigated before (baseline) and during chronic VNS treatment. The experiments were performed at two different stimulation intensities: 2 to 5 days after implantation at a low stimulation intensity (mean intensity 0.7 ± 0.2 mA, second session) and after 8 to 14 weeks of VNS therapy (mean intensity 1.4 ± 0.3 mA, third session). Twelve healthy age- and sex-matched subjects were investigated using the same experimental protocol. Itch was induced by histamineiontophoresis and quantified on a visual analogue scale (VAS). Histamine-induced flare was quantified using laserDoppler flowmetry.
Results: Itch was reduced by VNS from 24 ± 8% VAS at baseline to 15 ± 5% VAS at second session, and 19 ± 8% VAS at third session (p < 0.05 multivariate analysis of variance). In the control group, itch remained unaltered in all three sessions (26 ± 5% at baseline, 23 ± 5% in the second session, and 25 ± 5% in the third session, not significant). The flare was unaltered in both patients and control subjects.
Conclusions: VNS may suppress pruritus in humans.
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