Central opioidergic neurotransmission in complex regional pain syndrome.
OBJECTIVE
Complex regional pain syndrome (CRPS) is a chronic pain condition characterized by sensory, motor, and autonomic symptoms. It develops after limb trauma and may be associated with relevant psychiatric comorbidity. As there is evidence for central pathophysiology which might be related to an altered opioidergic neurotransmission, we investigated the cerebral opioid receptor status under resting conditions in this patient population.


METHODS
In this case-control study, 10 patients with CRPS and 10 age- and gender-matched healthy subjects underwent a PET scan using the subtype-nonselective opioidergic radioligand [(18)F]fluoroethyl-diprenorphine. As a surrogate for regional cerebral opioid receptor availability, the opioid receptor binding potential (OR-BP) was assessed by means of the modified Logan plot with reference region input for categorical group comparison and correlation with clinical data in the patient group.


RESULTS
Patients with CRPS showed reduced OR-BP in contralateral amygdala and parahippocampal gyri and increased OR-BP in contralateral prefrontal cortical areas. When OR-BP in the midcingulate cortex and the ipsilateral temporal cortex was low, the McGill pain rating index was high. In general, when anxiety and depression scales were high, contralateral temporal OR-BP was high as well. In addition, the anxiety scale decreased with increasing OR-BP in the contralateral parahippocampal cortex.


CONCLUSIONS
These results demonstrate altered central opioidergic neurotransmission in CRPS. The correlation of regional opioid receptor availability to measures of pain, anxiety, and depression underlines the clinical importance of these findings.
Klega
A
A
Department of Nuclear Medicine, Johannes Gutenberg University, Langenbeckstrasse 1, 55131 Mainz, Germany.
Eberle
T
T
Buchholz
H-G
HG
Maus
S
S
Maihöfner
C
C
Schreckenberger
M
M
Birklein
F
F
D000328:Adult; D000339:Affect; D001007:Anxiety / Q000523:psychology; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology; D001931:Brain Mapping; D016022:Case-Control Studies; D020918:Complex Regional Pain Syndromes / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology / Q000523:psychology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000000981:diagnostic imaging / Q000378:metabolism; D009483:Neuropsychological Tests; D010146:Pain / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology; D010147:Pain Measurement; D017288:Pain Threshold / Q000523:psychology; D011877:Radionuclide Imaging; D011957:Receptors, Opioid / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology
D011957:Receptors, Opioid