• Shigeki Omori, Sagiri Isose, Sonoko Misawa, Keisuke Watanabe, Yukari Sekiguchi, Kazumoto Shibuya, Minako Beppu, Hiroshi Amino, and Satoshi Kuwabara.
• Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan; Medical Corporation Jinseikai, Chiba, Japan.
• Neurosci. Res. 2017 Aug 1; 121: 43-48.

AbstractNeuropathic pain can result from neuronal hyperexcitability and complex interactions of the nociceptive pathways. Intraepidermal electrical stimulation (IES) is a novel technique that can selectively activate Aδ and C fibers. To investigate patterns of changes in Aδ- and C-mediated brain responses in patients with neuropathic pain using IES, we recorded pain-related evoked potential (PREP) after IES of Aδ and C fibers in 20 patients with neuropathic pain and 15 age-matched healthy volunteers. We evaluated PREP latencies, amplitudes, and amplitude ratios of PREPs after C/Aδ-fiber stimulation. PREP amplitudes after Aδ-fiber stimulation tended to be smaller in the patient group, whereas there were no significant differences in amplitudes after C-fiber stimulation between the patient and normal control groups. PREP amplitude ratios after C/Aδ-fiber stimulation were significantly greater in the patient group than in the control group, and the higher ratio tended to be associated with a greater visual analog scale score. Patients with neuropathic pain had a tendency towards decreased Aδ amplitudes and significantly increased C/Aδ PREP amplitude ratios and this ratio appeared to be associated with the intensity of pain. Our findings suggest that decreased inhibition of the Aδ to C nociceptive systems is associated with generation of neuropathic pain.Copyright © 2017 Elsevier Ireland Ltd and Japan Neuroscience Society. All rights reserved.

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