Large vessel vasculitis (LVV) and polymyalgia rheumatica (PMR) are both inflammatory rheumatic diseases that can result in serious illness if not diagnosed. Unfortunately, these conditions remain challenging to diagnose due to their nonspecific symptoms and the absence of pathognomonic laboratory findings. In recent years, 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has emerged as an essential tool in evaluating and managing LVV and PMR. This article aims to discuss the role of 18F-FDG PET/CT in the diagnosis, management, and follow-up of patients with LVV and PMR.
The Role of 18F-FDG PET/CT in Diagnosis
LVV encompasses a group of disorders, including giant cell arteritis (GCA) and Takayasu arteritis (TA), which involve the inflammation of the large arteries. PMR, conversely, is a clinical syndrome characterised by pain and stiffness in the shoulder and pelvic girdles. Although PMR and GCA may present as separate entities, there is significant overlap between these conditions, as approximately 40-60% of GCA patients may also have PMR symptoms.
Conventional diagnostic methods for LVV and PMR include laboratory tests such as erythrocyte sedimentation rate and C-reactive protein and modern imaging modalities like ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT). However, these tests may have limitations regarding sensitivity, specificity, and ability to detect disease activity.
18F-FDG PET/CT has shown promise in diagnosing LVV and PMR due to its ability to detect increased metabolic activity and inflammation in the affected vessels and musculoskeletal structures. In addition, it has demonstrated high sensitivity and specificity in diagnosing GCA and TA, with studies reporting sensitivity rates of 85-100% and specificity rates of 75-93%.
In PMR, 18F-FDG PET/CT has shown high sensitivity in detecting subclinical inflammation of the shoulder and pelvic girdles, which may aid in early diagnosis and initiation of therapy.
Optimising Management of Large Vessel Vasculitis and Polymyalgia Rheumatica
18F-FDG PET/CT can be crucial in managing LVV and PMR by assessing the extent of vascular involvement, evaluating response to treatment, and detecting complications. The extent of vascular involvement in LVV is an important determinant of treatment strategy and prognosis. 18F-FDG PET/CT can help identify the affected arteries and potential complications such as stenosis, occlusion, or aneurysm formation, allowing for tailored treatment approaches.
Monitoring treatment response is vital in managing LVV and PMR, as it can help guide therapy adjustments and prevent unnecessary treatment-related side effects. 18F-FDG PET/CT can be used to assess the effectiveness of treatment by evaluating changes in metabolic activity and inflammation in the affected structures. A decrease in 18F-FDG uptake after treatment initiation indicates a favourable response to therapy, while persistent or increased uptake may suggest the need for alternative treatments or further investigations.
Given the chronic and relapsing nature of LVV and PMR, long-term follow-up is necessary to monitor disease activity and detect relapses. 18F-FDG PET/CT can be used to monitor patients for disease recurrence, particularly in cases where clinical and laboratory findings are inconclusive. Early detection of relapse can prompt timely intervention and prevent disease progression and complications.
Conclusion
The role of 18F-FDG PET/CT in the diagnosis, management, and follow-up of large vessel vasculitis and polymyalgia rheumatica is invaluable. Its ability to detect increased metabolic activity and inflammation in affected vessels and musculoskeletal structures enables timely diagnosis and initiation of appropriate therapies. In addition, 18F-FDG PET/CT can help guide tailored treatment approaches and monitor for disease recurrence by assessing the extent of vascular involvement, evaluating treatment response, and detecting complications.
Although the growing evidence supporting the use of 18F-FDG PET/CT in evaluating LVV and PMR, specific challenges and limitations still exist. These include variability in image interpretation, patient factors such as age, glucose levels, and inflammatory comorbidities impact on 18F-FDG uptake and exposure to ionising radiation. To optimise 18F-FDG PET/CT in clinical practice, further research is needed to establish standardised protocols, improve image interpretation, and develop novel radiotracers with higher specificity for inflammation.
You are here: home »