Whole-Body 18F-FDG PET and 18F-FDG PET/CT in Patients with Suspected Paraneoplastic Syndrome: A Systematic Review and Meta-Analysis of Diagnostic Accuracy

The role of 18FDG-PET imaging in VEXAS syndrome: a multicentric case series and a systematic review of the literature

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, and somatic) syndrome is characterized by heterogeneous clinical manifestations. Due to the inflammatory nature of this condition, 18-FDG-PET (18-fluorodeoxyglucose-positron emission tomography) might be used to diagnose and monitor the disease. However, no data are available about the most common findings of PET imaging in this disease. For this reason, we summarised all the available reports of patients with VEXAS who underwent at least one PET scan and described 8 additional patients' PET from our centres. Overall, we described 35 patients' PET findings. All patients were male, with a median age of 70 years. The most frequent hypermetabolic sites on PET scans were the bone marrow (77.1%), lymph nodes (35.3%), lungs (28.6%), spleen and large vessels (22.9%), and cartilage (20%). Six patients underwent a PET scan 2.7 ± 1.5 years before VEXAS diagnosis, showing nonspecific uptake in the bone marrow. Four patients had a follow-up PET scan, showing a decrease or a disappearance of the previously identified hypermetabolic areas. In conclusion, although no specific uptake site has been found for VEXAS syndrome, PET imaging could help detect inflammatory foci that are not clinically evident. In addition, high metabolic activity in bone marrow might precede the clinical onset of the disease, shedding light on the pathogenesis of VEXAS.

Adult inflammatory leukoencephalopathies

Inflammatory white matter disorders may commonly mimic genetic leukoencephalopathies. These include atypical presentations of common conditions, such as multiple sclerosis, together with rare inflammatory disorders. A structured approach to such cases is essential, together with judicious use of the many available diagnostic biomarkers. The potential for such conditions to respond to immunotherapy emphasizes the importance of an accurate and prompt diagnosis in improving patient outcomes.

Clinical approach to diagnosis of paraneoplastic neurologic syndromes

The correct diagnosis of a paraneoplastic neurologic syndrome (PNS) first requires the identification of the syndrome as one of those defined as high-risk (previously called classical) or intermediate-risk for cancer in the 2021 PNS diagnostic criteria. Testing for neuronal antibodies should be restricted to these syndromes as indiscriminate request decreases the diagnostic value of the antibodies. Identifying onconeural (high-risk for cancer) or intermediate-risk for cancer antibodies supports the paraneoplastic diagnosis and mandates the search for an underlying cancer. Tumor screening must follow the published guidelines. Repeated screening is indicated in neurologic syndromes with onconeural antibodies and patients with high-risk for cancer neurologic syndromes unless they present neuronal antibodies which are not associated with cancer. Neuronal antibodies should be screened by immunohistochemistry and confirmed by immunoblot (intracellular antigens) or cell-based assay (CBA) (surface antigens). Positive results only by immunoblot or CBA should be taken with caution. Although the 2021 diagnostic criteria for PNS do not capture all PNS, as they do not allow to diagnose definite PNS neurologic syndromes without neuronal antibodies, the updated criteria represent a step forward to differentiate true PNS from neurologic syndromes that coincide in time with cancer diagnosis without having a pathogenic link.

Clinical value of [18F]F-FDG PET/CT in patients with suspected paraneoplastic dermatoses: Diagnostic performance and impact on clinical management

PURPOSE

We retrospectively evaluate the diagnostic performance of 2-deoxy-2[18F]fuoro-D-glucose([18F]F-FDG) PET/CT and its impact on clinical management in patients with suspected paraneoplastic dermatoses (PD).

MATERIALS AND METHODS

From an institutional PET/CT database (2014-2022), we retrospectively analyzed patients who were clinically suspected with PD and underwent [18F]F-FDG PET/CT for screening an underlying malignancy. For all scans, positive mucocutaneous lesions and PET-indicated malignancies were assessed, and the degree of FDG avidity among different dermatoses were quantified. The final diagnoses of dermatoses and neoplasms were based on pathologic results, international diagnostic standard and follow-up. We assessed the recommended and applied therapies before and after [18F]F-FDG PET/CT and noted whether the patient management changed on the basis of the [18F]F-FDG PET/CT results.

RESULTS

We analyzed 60 patients with 10 types of dermatoses in this study. Finally, 19 of the 60 patients who had both of specific dermatosis and contemporaneous neoplasm were diagnosed with PD. [18F]F-FDG PET could identify the underlying neoplasms in 18/19 (94.7%) PD patients, and led to a change of the management in 9/19 (47.4%) PD patients. In addition, the mucocutaneous manifestations of [18F]F-FDG PET/CT associated with several specific dermatoses were characteristic.

CONCLUSIONS

This study highlighted the value of [18F]F-FDG PET/CT as a useful tool for evaluation of patients with suspected PD to unveil the underlying culprit tumor, and profoundly supports the clinical management of PD patients.

Autoimmune Encephalitis and Related Syndromes

The field of autoimmune neurology has greatly expanded in the last decade [...].

Paraneoplastic Syndromes from Head to Toe: Pathophysiology, Imaging Features, and Workup

Patients often have symptoms due to the mass effect of a neoplasm on surrounding tissues or the development of distant metastases. However, some patients may present with clinical symptoms that are not attributable to direct tumor invasion. In particular, certain tumors may release substances such as hormones or cytokines or trigger an immune cross-reactivity between malignant and normal body cells, resulting in characteristic clinical features that are broadly referred to as paraneoplastic syndromes (PNSs). Recent advances in medicine have improved the understanding of the pathogenesis of PNSs and enhanced their diagnosis and treatment. It is estimated that 8% of patients with cancer develop a PNS. Diverse organ systems may be involved, most notably the neurologic, musculoskeletal, endocrinologic, dermatologic, gastrointestinal, and cardiovascular systems. Knowledge of various PNSs is necessary, as these syndromes may precede tumor development, complicate the patient's clinical presentation, indicate tumor prognosis, or be mistaken for metastatic spread. Radiologists should be familiar with the clinical presentations of common PNSs and the selection of appropriate imaging examinations. Many of these PNSs have imaging features that can assist with arriving at the correct diagnosis. Therefore, the key radiographic findings associated with these PNSs and the diagnostic pitfalls that can be encountered during imaging are important, as their detection can facilitate early identification of the underlying tumor, reveal early recurrence, and enable monitoring of the patient's response to therapy. © RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Oncologic emergencies and urgencies: A comprehensive review

Patients with advanced cancer generate 4 million visits annually to emergency departments (EDs) and other dedicated, high-acuity oncology urgent care centers. Because of both the increasing complexity of systemic treatments overall and the higher rates of active therapy in the geriatric population, many patients experiencing acute decompensations are frail and acutely ill. This article comprehensively reviews the spectrum of oncologic emergencies and urgencies typically encountered in acute care settings. Presentation, underlying etiology, and up-to-date clinical pathways are discussed. Criteria for either a safe discharge to home or a transition of care to the inpatient oncology hospitalist team are emphasized. This review extends beyond familiar conditions such as febrile neutropenia, hypercalcemia, tumor lysis syndrome, malignant spinal cord compression, mechanical bowel obstruction, and breakthrough pain crises to include a broader spectrum of topics encompassing the syndrome of inappropriate antidiuretic hormone secretion, venous thromboembolism and malignant effusions, as well as chemotherapy-induced mucositis, cardiomyopathy, nausea, vomiting, and diarrhea. Emergent and urgent complications associated with targeted therapeutics, including small molecules, naked and drug-conjugated monoclonal antibodies, as well as immune checkpoint inhibitors and chimeric antigen receptor T-cells, are summarized. Finally, strategies for facilitating same-day direct admission to hospice from the ED are discussed. This article not only can serve as a point-of-care reference for the ED physician but also can assist outpatient oncologists as well as inpatient hospitalists in coordinating care around the ED visit.

The role of [18F]FDG PET/CT in paraneoplastic autoimmune disorders: an umbrella review

Paraneoplastic autoimmune disorders (PAD) are a group of autoimmune diseases associated with neoplasms. Several evidence-based articles (systematic reviews and meta-analyses) have reported data about the role of positron emission tomography (PET) and related hybrid modalities (e.g., PET/CT) using 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) in patients with PAD. We performed an umbrella review of published systematic reviews and meta-analyses in this setting to provide an evidence-based summary and suggestions for further studies. Several databases were searched to find systematic reviews and meta-analysis on [18F]FDG PET/CT in PAD. Evidence-based data support the use of [18F]FDG PET/CT in patients with suspected PAD for investigating an underlying malignancy even if it is still unclear whether [18F]FDG PET/CT should be performed after negative/inconclusive conventional imaging or as part of the initial workup of PAD.

F-18-FDG PET/CT findings of paraneoplastic dermatoses

Paraneoplastic dermatoses (PD) are defined as nonspecific skin disorders which are associated with internal neoplasms, but without direct association to primary tumors or metastases. Recognition of PD and the following surveillance may lead to the diagnosis of internal malignant neoplasms including early stage ones. Accurate imaging examinations in the following searching is essential in identifying the underlying neoplasms. Since whole-body 18-fluoro-2-deoxyglucose (F-18-FDG)-positron emission (PET)/computed tomography (CT) has been widely used in early diagnosis, staging of various malignant tumors, it may play a role for detection of underlying or occult malignant neoplasms in patients with PD. However, to date, only a few reports of FDG PET/CT findings of the associated neoplasms in PD patients have been cited in the literature. The present paper shows the cases of FDG-avid associated neoplasms in patients with PD in our 10-year experience in our institute, and reviews the well-known and/or relatively common PD and their associated neoplasms, and the previously reported cases of FDG-avid associated neoplasms in these patients.

Additional Value of [18F]FDG PET/CT in Detection of Suspected Malignancy in Patients with Paraneoplastic Neurological Syndromes Having Negative Results of Conventional Radiological Imaging

Background: Paraneoplastic neurological syndromes (PNS) affecting the CNS (central nervous system) are rare, presenting in less than 1% of all those with cancer. The pathogenesis of paraneoplastic neurological syndromes is not fully understood, but it is presumed to result from an immune attack on the underlying malignancy. The presence of different types of onconeural antibodies may occur in different tumors and can lead to different clinical manifestations, making the early detection of cancers challenging. Aim: An evaluation of [18F]FDG PET/CT in neoplastic tumor detection in patients with paraneoplastic neurological syndromes having negative or unremarkable results of conventional radiological imaging. Methods: Among all patients diagnosed with paraneoplastic neurological syndromes in the Neurology Department in 2016–2020, 15 patients with unremarkable conventional radiological findings who underwent [18F]FDG PET/CT were included in the study. Results: [18F]FDG PET/CT enabled localization of suspected malignancy in 53% (8 of 15) of PNS cases with previous unremarkable conventional radiological findings. Conclusion: [18F]FDG PET/CT may be considered as a useful tool for neoplastic tumor detection in patients with paraneoplastic neurological syndromes, accelerating the diagnostic process and enabling faster initiation of appropriate treatment.

A proof-of-concept study on the use of a fluorescein-based 18F-tracer for pretargeted PET

Background

Pretargeted immuno-PET tumor imaging has emerged as a valuable diagnostic strategy that combines the high specificity of antibody-antigen interaction with the high signal and image resolution offered by short-lived PET isotopes, while reducing the irradiation dose caused by traditional ⁸⁹Zr-labelled antibodies. In this work, we demonstrate proof of concept of a novel ‘two-step’ immuno-PET pretargeting approach, based on bispecific antibodies (bsAbs) engineered to feature dual high-affinity binding activity for a fluorescein-based ¹⁸F-PET tracer and tumor markers.

Results

A copper(I)-catalysed click reaction-based radiolabeling protocol was developed for the synthesis of fluorescein-derived molecule [¹⁸F]TPF. Binding of [¹⁸F]TPF on FITC-bearing bsAbs was confirmed. An in vitro autoradiography assay demonstrated that [¹⁸F]TPF could be used for selective imaging of EpCAM-expressing OVCAR3 cells, when pretargeted with EpCAMxFITC bsAb. The versatility of the pretargeting approach was showcased in vitro using a series of fluorescein-binding bsAbs directed at various established cancer-associated targets, including the pan-carcinoma cell surface marker EpCAM, EGFR, melanoma marker MCSP (aka CSPG4), and immune checkpoint PD-L1, offering a range of potential future applications for this pretargeting platform.

Conclusion

A versatile pretargeting platform for PET imaging, which combines bispecific antibodies and a fluorescein-based ¹⁸F-tracer, is presented. It is shown to selectively target EpCAM-expressing cells in vitro and its further evaluation with different bispecific antibodies demonstrates the versatility of the approach.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41181-022-00155-2.

Utility of positron emission tomography-computed tomography in the evaluation of fever of unknown origin in a resource-limited tropical nation

Positron emission tomography–computed tomography (PET-CT) has been used as an imaging modality in workup of fever of unknown origin (FUO). The aim of our study is to evaluate the diagnostic utility of PET-CT in FUO workup in a resource-limited setting. We also looked at laboratory parameters as predictors of contributory PET-CT scans and propose an algorithm for evaluation of FUO in resource-limited tropical regions. This retrospective observational study included patients admitted for FUO workup under general medicine in a teaching hospital in South India from June 2013 to May 2016. PET-CT was done when the patient remained undiagnosed after a detailed clinical assessment and first- and second-tier investigations. Among 43 patients included in our study, a definite diagnosis was established in 74% (32). Noninfectious inflammatory diseases, infections, malignancies, and miscellaneous diseases were diagnosed in 37.2% (16/43), 23.3% (10/43), 9.3% (4/43), and 4.7% (2/43), respectively. Tuberculosis was the single most common disease seen in 20.9% (9/43). PET-CT scans were contributory toward establishment of final diagnosis in 90.7% (39/43). High C-reactive protein (CRP) and aspartate aminotransferase (AST) levels were associated with contributory PET-CT scans (P = 0.006 and 0.011, respectively). PET-CT delineating organ/tissue for diagnostic biopsy was associated with final diagnosis of infectious disease (P = 0.001). Sensitivity, specificity, and positive and negative predictive value of PET-CT scans were 76.9% (20/26), 33.3% (2/6), 83% (20/24), and 25% (2/8), respectively. High CRP and AST were predictors of contributory PET-CT scans. PET-CT scans have high sensitivity and positive predictive value when used in evaluation of FUO. Although it is a useful tool in FUO workup, especially in the diagnosis of tropical infections, PET-CT should be done after a comprehensive clinical assessment and basic investigations.

Decrease in the cortex/striatum metabolic ratio on [18F]-FDG PET: a biomarker of autoimmune encephalitis

PURPOSE

The aim of this [¹⁸F]-FDG PET study was to determine the diagnostic value of the cortex/striatum metabolic ratio in a large cohort of patients suffering from autoimmune encephalitis (AE) and to search for correlations with the course of the disease.

METHODS

We retrospectively collected clinical and paraclinical data of patients with AE, including brain ¹⁸F-FDG PET/CT. Whole-brain statistical analysis was performed using SPM8 software after activity parametrization to the striatum in comparison to healthy subjects. The discriminative performance of this metabolic ratio was evaluated in patients with AE using receiver operating characteristic curves against 44 healthy subjects and a control group of 688 patients with MCI. Relationship between cortex/striatum metabolic ratios and clinical/paraclinical data was assessed using univariate and multivariate analysis in patients with AE.

RESULTS

Fifty-six patients with AE were included. In comparison to healthy subjects, voxel-based statistical analysis identified one large cluster (p-cluster < 0.05, FWE corrected) of widespread decreased cortex/striatum ratio in patients with AE. The mean metabolic ratio was significantly lower for AE patients (1.16 ± 0.13) than that for healthy subjects (1.39 ± 0.08; p < 0.001) and than that for MCI patients (1.32 ± 0.11; p < 0.001). A ratio threshold of 1.23 allowed to detect AE patients with a sensitivity of 71% and a specificity of 82% against MCI patients, and 98% against healthy subjects. A lower cortex/striatum metabolic ratio had a trend towards shorter delay before ¹⁸F-FDG PET/CT (p = 0.07) in multivariate analysis.

CONCLUSION

The decrease in the cortex/striatal metabolic ratio has a good early diagnostic performance for the differentiation of AE patients from controls.

Weight loss as primary indication for FDG-PET/CT

PURPOSE

Some consider fluorodeoxyglucose positron emission tomography with computed tomography (FDG-PET/CT) clinically useful in patients presenting with nonspecific symptoms of malignancy, weight loss most commonly encountered. However, the appropriateness of such FDG-PET/CT studies remains to be clarified. This study evaluated the clinical value of FDG-PET/CT in patients referred primarily for weight loss.

METHODS

From 2010 to 2017 in one academic center, 252 subjects underwent 254 FDG-PET/CT studies for weight loss as primary indication and retrospectively studied. Eighteen subjects were excluded due to ongoing active malignancy, weight loss not ultimately being the main indication for the FDG-PET/CT, technically inadequate FDG-PET/CT and insufficient follow-up. The FDG-PET/CT scans were considered clinically beneficial when true positive for the cause of weight loss that other investigations missed or would have missed, clinically neutral when true negative and clinically detrimental when false positive leading to additional investigations or false negative.

RESULTS

Ultimately 234 unique subjects (236 FDG-PET/CT studies) were included. The average subject weight loss prior to the PET was 12 kg and average follow-up time post FDG-PET/CT scan was 3.4 years. The FDG-PET/CT scans were true positive in 24 studies (10%) with 8 studies (3%) clinically beneficial; false positive in 38 studies (16%) of which 26 led to 35 additional procedures and false negative in 13 studies (6%). In total, 39 (17%) FDG-PET/CT studies were clinically detrimental. The other 149 (63%) studies were true negative, clinically neutral.

CONCLUSION

FDG-PET/CT appears to have limited value in assessing subjects with weight loss as the leading clinical indication, proving to be five times more often detrimental than beneficial.

18F-fluorodeoxyglucose positron emission tomography/ computed tomography in the diagnosis of suspected paraneoplastic syndromes: A retrospective analysis

Paraneoplastic syndromes are a rare clinical presentation of tumor thought to affect 0.01% of patients with cancer. Paraneoplastic syndromes present a diagnostic challenge as a wide variety of signs and symptoms may appear. This study examines the use of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) as a diagnostic imaging tool for detecting tumor in suspected paraneoplastic syndrome cases. This single-center retrospective study included patients with suspected paraneoplastic syndrome who underwent whole-body ¹⁸F-FDG PET/CT scan between December 2005 and December 2016. Associated clinical data were gathered via electronic chart review. Patient records were reviewed for age, sex, clinical signs and symptoms, ancillary diagnostic procedures, date of diagnosis, and follow-up time. Ninety-nine patients met inclusion criteria for this study. Mean follow-up period was 1.8 years. Cancer prevalence was 12.1%. The ¹⁸F-FDG PET/CT results are as follows: 10 true positives, 5 false positives, 82 true negatives, and 2 false negatives. The diagnostic values are as follows: sensitivity 83.3%, specificity 94.3%, positive predictive value 66.7%, and negative predictive value (NPV) 97.6%. The high NPV in our study supports the effectiveness of ¹⁸F-FDG PET/CT to rule out tumor in suspected paraneoplastic syndrome. Future research aims to analyze which patients with suspected paraneoplastic syndrome would benefit most from ¹⁸F-FDG PET/CT.

Update on PET in neurodegenerative and neuroinflammatory disorders manifesting on a behavioural level: imaging for differential diagnosis

PURPOSE OF REVIEW

To give an update on recent findings concerning the use of PET for differential diagnosis in neurodegenerative and neuroinflammatory disorders manifesting on a behavioural level.

RECENT FINDINGS

Although accurate differential diagnosis of dementia can be achieved by imaging disease-specific patterns of cerebral glucose metabolism with [F]fluorodeoxyglucose ([F]FDG)-PET, the diagnostic impact of [F]FDG-PET in primary psychiatric disorders is limited. Amyloid-beta PET provides an incremental value beyond [F]FDG-PET in the differential diagnosis of dementia and was proposed as a biomarker defining the so-called Alzheimer continuum. Recently developed tau-specific tracers might also aid in the diagnostic process (biological definition of Alzheimer's disease together with amyloid-beta). Surpassing the diagnostic accuracy of other techniques, such as MRI, [F]FDG-PET has also gained widespread clinical use for diagnosis and follow-up of paraneoplastic and autoimmune disorders of the central nervous system (CNS) as an important differential diagnosis for rapid progressive dementia and subacute onset of psychiatric syndromes.

SUMMARY

Molecular neuroimaging with PET is an established method for the differential diagnosis of neurodegenerative and autoimmune CNS disorders manifesting on a behavioural level with significant therapeutic and prognostic impact. Future prospective studies are needed to define the value of tau imaging for diagnosis and prognosis in neurodegenerative disorders.

18F-FDG PET/CT in a Patient With Thymoma-Associated Paraneoplastic Polymyositis

A 43-year-old woman presented with progressive muscle weakness and myalgia for 1 month. Laboratory tests revealed the elevation of myogenic enzymes. MRI of the thighs demonstrated a pattern of edema for inflammatory myopathy. Electromyography showed diffuse myopathic disorder, and muscle biopsy indicated polymyositis. F-FDG PET/CT was performed to investigate the potential paraneoplastic syndrome and revealed a soft tissue lesion with F-FDG avidity in the right anterior mediastinum, as well as diffusely increased activity throughout the body muscles. The patient's symptoms and biochemical abnormalities were gradually relieved after the tumor resection, and the histopathology indicated a type AB thymoma.

Cancer frequency detected by positron emission tomography-computed tomography in limbic encephalitis

OBJECTIVE

Paraneoplastic limbic encephalitis (LE) occurs frequently with considerable variability according to literature reports. We thus determined the cancer frequency in mixed LE subtypes sharing the diagnosis of temporal lobe epilepsy (TLE).

METHODS

All patients underwent magnetic resonance imaging (MRI) of the brain, electroencephalography (EEG) recordings, neuropsychological testing, immunohistochemistry, and clinical examination together with whole body 2-fluor-2-desoxy-d-glucose (FDG)-positron emission tomography (PET)/computed tomography (CT) to detect cancer in this observatory study.

RESULTS

Ninety-three patients (median: 52 years) with TLE due to autoimmune LE were investigated. Cancer was detected in the FDG-PET/CTs of 3 out of 93 (3.2%) patients with LE. Cancer was diagnosed upon, 5 years earlier and 5 years after FDG-PET/CT in 7 of 93 (7.5%) of all patients with LE. The cancer frequency in those patients was significantly lower than that reported in the largest series of patients with LE associated with and without different antibodies (7.5% vs. 23.5%, Bootstrap test, p < 0.05), but was indistinguishable from the estimated age-dependent cancer frequency in the German regional North-Rhine-Westfalian population without LE in 2014 (Chi-square test: p = 0.2).

CONCLUSIONS

Our findings reveal that the cancer frequency in patients with TLE with LE detected by FDG-PET/CT is low and not different from the age-dependent natural cancer occurrence in a regional population.

Pragmatic Treatment of Stiff Person Spectrum Disorders

Background

Stiff person spectrum disorders (SPSD) are a group of rare conditions clinically characterized by stiffness, spasms, and heightened stimulus sensitivity. They also share a spectrum of antibodies.

Methods

We reviewed the literature and our own experience with the aim of providing a practical approach to the treatment of SPSD.

Results

Because of the rarity of SPSD, there is little evidence to guide treatment decisions. The treatment of SPSD is based on the triad of symptomatic treatment, immunotherapy, and tumor treatment where appropriate. Moreover, the management involves continuous and appropriate monitoring of the symptoms of the disease, its autoimmune associations, and potential treatment side effects.

Conclusions

Here we delineated a pragmatic treatment approach to SPSD, based on our experience and existing literature. We also highlighted how our understanding of neuronal antibodies and their implications reflects on management considerations.

[From stiff man syndrome to stiff person spectrum disorders]

The identification of new variants of the stiff man syndrome (SMS) and of new, probably pathogenic neuronal autoantibodies has led to the concept of stiff man (or person) spectrum disorders (SPSD). This is an expanding group of rare chronic autoimmune inflammatory diseases of the central nervous system (CNS) that have in common the main symptoms of fluctuating rigidity and spasms with pronounced stimulus sensitivity. These core symptoms are mandatory and can be accompanied by a wide variety of other neurological signs. The SPSDs are associated with autoantibodies directed against neuronal proteins that attenuate excitability. Neither clinical phenotypes nor the course of SPSD correlate closely with the antibody status. The treatment of these diseases aims at maintaining mobility and is pragmatically oriented to the degree of impediment and comprises antispastic, anticonvulsant and immunomodulating or immunosuppressive medication strategies.

Diagnostic Value of Positron Emission Tomography Combined with Computed Tomography for Evaluating Critically Ill Neurological Patients

Purpose

¹⁸F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) is a promising new tool for the identification of inflammatory, infectious, and neoplastic foci. The aim of our work was to evaluate the diagnostic value of FDG-PET/CT in patients treated on a neurological/neurosurgical ICU or stroke unit.

Methods

We performed a single-center, 10-year, retrospective evaluation of the value of FDG-PET/CT in critically ill adult patients with severe neurological disease.

Results

42 patients underwent FDG-PET/CT. Of these, 15 were ventilated and 10 were under vasopressor support. We identified four indications for performing FDG-PET/CT: (1) excluding a paraneoplastic etiology in an otherwise unexplained encephalitis, encephalopathy or neuropathy, (2) detecting a large-vessel vasculitis in patients with ischemic stroke, (3) detecting an infectious focus in sepsis, and less frequently (4) evaluating cerebral metabolism. In 22 patients who were evaluated for an unknown malignancy, 5 scans revealed either a previously unknown tumor or unknown metastases of a previously treated malignancy. Of 11 patients investigated for large-vessel vasculitis, 2 showed an inflammation of arteries supplying the brain. Of six sepsis cases, FDG-PET/CT identified an infectious focus in four.

Summary

We found FDG-PET/CT to be a helpful tool in critically ill neurological patients. The results of the FDG-PET/CT had direct therapeutic consequences in the 12 true-positive cases. In 24 of the 29 negative cases, FDG-PET/CT helped exclude alternative diagnoses and/or influenced therapy. Our findings demonstrate the feasibility and diagnostic benefit of FDG-PET/CT in this group of patients.