Pain-related evoked potentials after intraepidermal electrical stimulation to Aδ and C fibers in patients with neuropathic pain.
Neuropathic 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.
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan; Medical Corporation Jinseikai, Chiba, Japan.
Shigeki
S
Omori
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan; Department of Neurology, National Hospital Organization Chiba-East Hospital, Chiba, Japan. Electronic address: sagiri-i@par.odn.ne.jp.
Sagiri
S
Isose
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Sonoko
S
Misawa
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Keisuke
K
Watanabe
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Yukari
Y
Sekiguchi
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Kazumoto
K
Shibuya
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Minako
M
Beppu
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Hiroshi
H
Amino
Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Satoshi
S
Kuwabara
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D009437:Neuralgia / Q000473:pathology* / Q000503:physiopathology*; D011930:Reaction Time; D012684:Sensory Thresholds / Q000502:physiology; D012867:Skin / Q000294:innervation*; D013223:Statistics as Topic; D064232:Visual Analog Scale
Aδ-fiber; C-fiber; Intraepidermal electrical stimulation; Neuropathic pain; Pain-related evoked potentials; Small fiber