Successful treatment of chronic knee pain following localization by a sigma-1 receptor radioligand and PET/MRI: a case report

Abstract

Peter William Cipriano,1 Sheen-Woo Lee,1,2 Daehyun Yoon,1 Bin Shen,1 Vivianne Lily Tawfik,3 Catherine Mills Curtin,4 Jason L Dragoo,5 Michelle Louise James,1 Christopher Robert McCurdy,6 Frederick Te-Ning Chin,1 Sandip Biswal1 1Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA; 2Department of Radiology, Gachon University Gil Hospital, Incheon, South Korea; 3Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, CA, USA; 4Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA, USA; 5Department of Orthopedic Surgery, Stanford University School of Medicine, Stanford, CA, USA; 6Clinical and Translational Science Institute, Translational Drug Development Core, University of Florida, Gainesville, FL, USA Background: The ability to accurately diagnose and objectively localize pain generators in chronic pain sufferers remains a major clinical challenge since assessment relies on subjective patient complaints and relatively non-specific diagnostic tools. Developments in clinical molecular imaging, including advances in imaging technology and radiotracer design, have afforded the opportunity to identify tissues involved in pain generation based on their pro-nociceptive condition. The sigma-1 receptor (S1R) is a pro-nociceptive receptor upregulated in painful, inflamed tissues, and it can be imaged using the highly specific radioligand 18F-FTC-146 with PET. Case presentation: A 50-year-old woman with a 7-year history of refractory, left-knee pain of unknown origin was referred to our pain management team. Over the past several years, she had undergone multiple treatments, including a lateral retinacular release, radiofrequency ablation of a peripheral nerve, and physical therapy. While certain treatments provided partial relief, her pain would inevitably return to its original state. Using simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) with the novel radiotracer 18F-FTC-146, imaging showed increased focal uptake of 18F-FTC-146 in the intercondylar notch, corresponding to an irregular but equivocal lesion identified in the simultaneously acquired MRI. These imaging results prompted surgical removal of the lesion, which upon resection was identified as an inflamed, intraarticular synovial lipoma. Removal of the lesion relieved the patient’s pain, and to date the pain has not recurred.Conclusion: We present a case of chronic, debilitating knee pain that resolved with surgery following identification of the pathology with a novel clinical molecular imaging approach that detects chronic pain generators at the molecular and cellular level. This approach has the potential to identify and localize pain-associated pathology in a variety of chronic pain syndromes. Keywords: PET/MRI, sigma-1 receptor, chronic pain, knee pain, molecular imaging, intraarticular synovial lipoma, 18F-FTC-146

Keywords

• PET/MRI
• sigma-1 receptor
• chronic pain
• knee pain
• molecular imaging
• intraarticular synovial lipoma
• 18F-FTC-146