Measurement of changes in opioid receptor binding in vivo during trigeminal neuralgic pain using [C-11]diprenorphine and positron emission tomography

The binding of [C-11]diprenorphine to mu, kappa, and delta subsites in cort ical and subcortical structures was measured by positron emission tomograph y in vivo in six patients before and after surgical relief of trigeminal ne uralgia pain. The volume of distribution of [C-11]diprenorphine binding was significantly increased after thermocoagulation of the relevant trigeminal division in the following areas: prefrontal, insular, perigenual, mid-cing ulate and inferior parietal cortices, basal ganglia, and thalamus bilateral ly. In addition to the pain relief associated with the surgical procedure, there also was an improvement in anxiety and depression scores. In the cont ext of other studies, these changes in binding most likely resulted from th e change in the pain state. The results suggest an increased occupancy by e ndogenous opioid peptides during trigeminal pain but cannot exclude coexist ent down-regulation of binding sites.