• Joseph Maarrawi, Roland Peyron, Patrick Mertens, Nicolas Costes, Michel Magnin, Marc Sindou, Bernard Laurent, and Luis Garcia-Larrea.
• Central Integration of Pain, Lyon Neuroscience Research Center, Lyon, France Laboratory of Neurosciences, St. Joseph University, Beirut, Lebanon Department of Functional Neurosurgery, Hôpital Neurologique, Lyon, France Department of Neurology and Pain center, Hôpital Nord, St-Etienne, France CERMEP Imagerie du vivant, Lyon, France Department of Anatomy, Claude Bernard University, Lyon, France.
• Pain. 2013 Nov 1; 154 (11): 2563-2568.

AbstractThe clinical effects of motor cortex stimulation (MCS) for neuropathic pain (NP) is thought to be mediated primarily by the secretion of endogenous opioids in humans and in animal models. Because opioid receptor density is itself decreased in patients with NP, we investigated whether the magnitude and distribution of the remaining opioid receptors in patients with NP could be biological predictors of the pain-relieving effects of MCS. Using (11)C-diprenorphine positron emission tomography scans, opioid receptor availability was assessed in 15 patients suffering refractory NP, who subsequently received chronically implanted MCS. All patients underwent 2 preoperative baseline scans at 2-wk intervals and were clinically assessed after 7mo of chronic MCS. The levels of preoperative opioid-binding in the insula, thalamus, periaqueductal gray, anterior cingulate, and orbitofrontal cortex were significantly and positively correlated with postoperative pain relief at 7mo. Patients with receptor density values below the lower limits in age-matched controls in the thalamus, periaqueductal gray and contralateral insula were the least likely to benefit from MCS. Opioid-receptor availability as shown in preoperative positron emission tomography scans appears to be related to the efficacy of MCS in NP and may help clinicians to select the candidates most likely to benefit from this procedure. Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

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