Visualization of painful inflammation in patients with pain after traumatic ankle sprain using [(11)C]-D-deprenyl PET/CT.

• BACKGROUND AND AIMS: Positron emission tomography (PET) with the radioligand [(11)C]-D-deprenyl has shown increased signal at location of pain in patients with rheumatoid arthritis and chronic whiplash injury. The binding site of [(11)C]-D-deprenyl in peripheral tissues is suggested to be mitochondrial monoamine oxidase in cells engaged in post-traumatic inflammation and tissue repair processes. The association between [(11)C]-D-deprenyl uptake and the transition from acute to chronic pain remain unknown. Further imaging studies of musculoskeletal pain at the molecular level would benefit from establishing a clinical model in a common and well-defined injury in otherwise healthy and drug-naïve subjects. The aim of this study was to investigate if [(11)C]-D-deprenyl uptake would be acutely elevated in unilateral ankle sprain and if tracer uptake would be reduced as a function of healing, and correlated with pain localizations and pain experience.METHODS: Eight otherwise healthy patients with unilateral ankle sprain were recruited at the emergency department. All underwent [(11)C]-D-deprenyl PET/CT in the acute phase, at one month and 6-14 months after injury.RESULTS: Acute [(11)C]-D-deprenyl uptake at the injury site was a factor of 10.7 (range 2.9-37.3) higher than the intact ankle. During healing, [(11)C]-D-deprenyl uptake decreased, but did not normalize until after 11 months. Patients experiencing persistent pain had prolonged [(11)C]-D-deprenyl uptake in painful locations.CONCLUSIONS AND IMPLICATIONS: The data provide further support that [(11)C]-D-deprenyl PET can visualize, quantify and follow processes in peripheral tissue that may relate to soft tissue injuries, inflammation and associated nociceptive signaling. Such an objective correlate would represent a progress in pain research, as well as in clinical pain diagnostics and management.

Nyckelord

Ankle injuries

Carbon-11

Deprenyl

Inflammation

PET

Pain

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