F-18 FDG PET/CT of polymyalgia rheumatica

PET/CT imaging in polymyalgia rheumatica: praepubic 18F-FDG uptake correlates with pectineus and adductor longus muscles enthesitis and with tenosynovitis

Background

The role of ¹⁸F-fluorodeoxyglucose positron emission computed tomography (¹⁸F-FDG PET/CT) is increasing in the diagnosis of polymyalgia rheumatica (PMR), one of the most common inflammatory rheumatic diseases. In addition to other locations, increased ¹⁸F-FDG accumulation has been detected in the praepubic region in some patients. However, a deeper description and pathophysiological explanation of this increased praepubic accumulation has been lacking. The aim of the presented study is to confirm a decrease in praepubic ¹⁸F-FDG accumulation in response to therapy and to describe potential correlations to other ¹⁸F-FDG PET/CT scan characteristics during the course of disease. As a secondary objective, we describe the pathological aspects of the observed praepubic ¹⁸F-FDG uptake.

Patients and methods

A retrospective review of patients with newly suspected PMR undergoing baseline and follow up ¹⁸F-FDG PET/CT between February 2010 and March 2016 is given. Those with a visually detected presence of praepubic ¹⁸F-FDG accumulation were further analysed. The uptake was assessed visually and also semi-quantitatively in the defined region of interest by calculation of target-to-liver ratios. Other regions typical for PMR were systematically described as well (shoulders, hips, sternoclavicular joints, ischiogluteal bursae, spinous interspaces).

Results

Twenty-three out of 89 screened patients (26%) presented with initial praepubic ¹⁸F-FDG PET/CT positivity, 15 of whom also underwent follow up ¹⁸F-FDG PET/CT examination. Five out of 15 patients presented with increased ¹⁸F-FDG accumulation in large arteries as a sign of giant cell arteritis. During follow up examination, decrease in ¹⁸F-FDG accumulation caused by therapeutic intervention was observed in all evaluated locations in all analysed patients and no new positivity was indicated, including periarticular, extraarticular tissues or target large vessels. Praepubical accumulation of ¹⁸F-FDG was diminished in all patients (15/15, 100%) after treatment with steroids.

Conclusions

Increased praepubic ¹⁸F-FDG uptake in patients with PMR is relatively common and this region should be systematically evaluated during differential diagnosis of rheumatic and malignant disease. Praepubic inflammation is probably related to enthesitis and tenosynovitis at the origin of pectineus and adductor longus muscles ventrally from the pubis.

The role of 18F-FDG PET/CT in large-vessel vasculitis: appropriateness of current classification criteria?

Patients with clinical suspicion of large-vessel vasculitis (LVV) may present with nonspecific signs and symptoms and increased inflammatory parameters and may remain without diagnosis after routine diagnostic procedures. Both the nonspecificity of the radiopharmaceutical ¹⁸F-FDG and the synergy of integrating functional and anatomical images with PET/CT offer substantial benefit in the diagnostic work-up of patients with clinical suspicion for LVV. A negative temporal artery biopsy, an ultrasonography without an arterial halo, or a MRI without aortic wall thickening or oedema do not exclude the presence of LVV and should therefore not exclude the use of ¹⁸F-FDG PET/CT when LVV is clinically suspected. This overview further discusses the notion that there is substantial underdiagnosis of LVV. Late diagnosis of LVV may lead to surgery or angioplasty in occlusive forms and is often accompanied by serious aortic complications and a fatal outcome. In contrast to the American College of Rheumatology 1990 criteria for vasculitis, based on late LVV effects like arterial stenosis and/or occlusion, ¹⁸F-FDG PET/CT sheds new light on the classification of giant cell arteritis (GCA) and Takayasu arteritis (TA). The combination of these observations makes the role of ¹⁸F-FDG PET/CT in the assessment of patients suspected for having LVV promising.

Polymyalgia rheumatica and interspinous FDG uptake on PET/CT

Polymyalgia rheumatica (PMR) is an inflammatory disease with macrophage infiltration and CD4+ T-lymphocytes-related mild synovitis commonly causing neck, shoulder, and hip stiffness in patients older than 50 years. Closely related to giant cell arthritis (GCA), PMR symptoms can be similar to rheumatoid arthritis. Erythrocyte sedimentation rate and C-reactive protein levels are elevated in >90% of cases. In 4 patients with PMR, (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) demonstrates uptake in the shoulder and hip joints and also interspinous and supraspinous focal and diffuse uptake. We propose diffuse uptake may reflect ligament inflammation with focal uptake in adjacent interspinous bursitis.

Parameters related to a positive test result for FDG PET(/CT) for large vessel vasculitis: a multicenter retrospective study

The purpose of this study was to identify clinical and laboratory parameters that may improve the effectiveness of the use of fluorodeoxyglucose positron emission tomography ((18)F-FDG PET)(/CT) for diagnosing large vessel vasculitis (LVV), and secondarily to assess the contribution of (18)F-FDG PET/CT in finding other diagnoses for patients without signs of LVV on the scan. A multicenter retrospective study of (18)F-FDG PET(/CT) scans performed between January 2000 and December 2009 for clinical suspicion of LVV was conducted. A total of 304 (18)F-FDG PET(/CT) scans were included, of which 62 (20%) were positive and 242 (80%) were negative for LVV. Univariate analysis showed that patients with a positive scan were older (65.9 ± 13.4 versus 58.6 ± 16.5 years, p = 0.002), were more frequently female (76% versus 55%, p = 0.002), more often had a history of temporal arteritis (10% versus 3%, p = 0.044), less frequently had artralgia (31% versus 67%, p = 0.000), and had higher thrombocyte counts (434 ± 161 versus 373 ± 168 × 10(9)/l, p = 0.049) and a higher erythrocyte sedimentation rate (ESR) (72.6 ± 31.0 versus 51.4 ± 30.5 mm/h, p = 0.001) than patients with a negative scan. In the multivariate analysis, only artralgia (OR 0.091; 95% CI 0.023-0.366) and ESR (OR 1.024; 95% CI 1.002-1.046) remained statistically significant predictors. The presence of artralgia is a statistically significant negative predictor and an elevated ESR a statistically significant positive predictor of LVV showing up on (18)F-FDG PET(/CT). A reliable prediction of the outcome of the scan, based on these two parameters, is not possible however. (18)F-FDG PET(/CT) allows early diagnosis of LVV and may discover occult inflammatory or neoplastic disorders.