EEG markers of pain suppression as a result of electrical stimulation: case report

Amputees often experience chronic neuropathic pain in their phantom limbs. Fortunately, this pain can be sup-pressed by electrical stimulation applied to peripheral nerves. Yet, neuronal correlate of the presence or absence of pain under these conditions is not well understood. Here we show that multichannel EEG can be used a biomarker of pain. We recorded and analyzed EEG data from two patients suffering from phantom limb pain. The recordings were conducted during a pain-relieving stimulation and in its absence. In both patients we observed a decrease in alpha power when the pain was suppressed by stimulation. Individual differences were observed, as well. In one patient the alpha power effects were prominent in the parietal sites whereas in the other in the somatosensory cortex bilaterally. Thus, modulations of alpha power could be used as a biomarker of pain in amputees, and such a biomarker could be useful for pain monitoring, as well as building closed-loop pain-relieving systems that operate automatically.