Article

Motor cortex stimulation (MCS) for neuropathic pain control induces
focal cerebral blood flow changes involving regions with high density of opioid
receptors. We studied the possible contribution of the endogenous opioid system
to MCS-related pain relief. METHODS: Changes in opioid receptor availability
induced by MCS were studied with PET scan and [(11)C]diprenorphine in eight
patients with refractory neuropathic pain. Each patient underwent two
preoperative (test-retest) PET scans and one postoperative PET scan acquired
after 7 months of chronic MCS. RESULTS: The two preoperative scans, performed at
2 weeks interval, did not show significant differences. Conversely, postoperative
compared with preoperative PET scans revealed significant decreases of
[(11)C]diprenorphine binding in the anterior middle cingulate cortex (aMCC),
periaqueductal gray (PAG), prefrontal cortex, and cerebellum. Binding changes in
aMCC and PAG were significantly correlated with pain relief. CONCLUSION: The
decrease in binding of the exogenous ligand was most likely explained by receptor
occupancy due to enhanced secretion of endogenous opioids. Motor cortex
stimulation (MCS) may thus induce release of endogenous opioids in brain
structures involved in the processing of acute and chronic pain. Correlation of
this effect with pain relief in at least two of these structures supports the
role of the endogenous opioid system in pain control induced by MCS.

Langue : ANGLAIS