Abstract
BackgroundHigh Frequency electrical Stimulation (HFS) of the skin induces enhanced brain responsiveness expressed as enhanced Event-Related Potential (ERP) N1 amplitude to stimuli applied to the surrounding unconditioned skin in healthy volunteers. The aim of the present study was to investigate whether this enhanced ERP N1 amplitude could be a potential marker for altered cortical sensory processing in patients with persistent pain after surgery.Materials and MethodsNineteen male patients; 9 with and 10 without persistent pain after inguinal hernia repair received HFS. Before, directly after and thirty minutes after HFS evoked potentials and the subjective pain intensity were measured in response to electric pain stimuli applied to the surrounding unconditioned skin.ResultsThe results show that, thirty minutes after HFS, the ERP N1 amplitude observed at the conditioned arm was statistically significantly larger than the amplitude at the control arm across all patients. No statistically significant differences were observed regarding ERP N1 amplitude between patients with and without persistent pain. However, thirty minutes after HFS we did observe statistically significant differences of P2 amplitude at the conditioned arm between the two groups. The P2 amplitude decreased in comparison to baseline in the group of patients with pain.ConclusionThe ERP N1 effect, induced after HFS, was not different between patients with vs. without persistent pain. The decreasing P2 amplitude was not observed in the patients without pain and also not in the previous healthy volunteer study and thus might be a marker for altered cortical sensory processing in patients with persistent pain after surgery.
Highlights
High Frequency electrical Stimulation (HFS) of peptidergic primary C-fiber afferents induces Long-Term Potentiation (LTP) of excitatory synaptic transmission between these C-fibers and secondary lamina I dorsal horn neurons projecting to the parabrachial area in the brainstem [1,2,3]
The results show that, thirty minutes after HFS, the Event-Related Potential (ERP) N1 amplitude observed at the conditioned arm was statistically significantly larger than the amplitude at the control arm across all patients
The decreasing P2 amplitude was not observed in the patients without pain and not in the previous healthy volunteer study and might be a marker for altered cortical sensory processing in patients with persistent pain after surgery
Summary
High Frequency electrical Stimulation (HFS) of peptidergic primary C-fiber afferents induces Long-Term Potentiation (LTP) of excitatory synaptic transmission between these C-fibers and secondary lamina I dorsal horn neurons projecting to the parabrachial area in the brainstem [1,2,3]. As a consequence, these neurons show enhanced responsiveness to normal afferent input. High Frequency electrical Stimulation (HFS) of the skin induces enhanced brain responsiveness expressed as enhanced Event-Related Potential (ERP) N1 amplitude to stimuli applied to the surrounding unconditioned skin in healthy volunteers. The aim of the present study was to investigate whether this enhanced ERP N1 amplitude could be a potential marker for altered cortical sensory processing in patients with persistent pain after surgery
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