Utility of 18F-FDG-PET/CT in patients suspected of paraneoplastic neurological syndrome: importance of risk classification

Anti-Ri paraneoplastic neurological syndrome presenting with bilateral cranial nerve VI palsy and jaw dystonia-a distinctive syndrome within the anti-Ri spectrum? : Case report and literature review

OBJECTIVE

Paraneoplastic neurological syndromes (PNS) are rare disorders associated with various onconeuronal antibodies. Anti-Ri antibodies (ANNA-2) are typically found in patients with opsoclonus myoclonus syndrome (OMS) and ataxia.

CASE REPORT

We present an anti-Ri antibody-positive 77-year-old woman with subacute progressive bilateral cranial nerve VI palsy, gait disturbance and jaw dystonia. MRI of the brain showed hyperintense signals on T2 bitemporal without contrast enhancement. Cerebrospinal fluid (CSF) examination exhibited mild pleocytosis of 13 cells/µl and positive oligoclonal bands. CSF was overall inconspicuous for a malignant or inflammatory etiology. Immunofluorescence analysis revealed anti-Ri antibodies in both serum and CSF. Subsequent diagnostic work up resulted in a newly diagnosed ductal carcinoma of the right breast. PNS in this case partially responded to the anti-tumor therapy.

CONCLUSION

This case shows similarities with recently published anti-Ri syndromes, which might form a distinct triad within the anti-Ri spectrum.

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.

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.

N-Methyl-d-aspartate Receptor Antibody Encephalitis: A Concise Review of the Disorder, Diagnosis, and Management

Anti-NMDA ( N-methyl-d-aspartate) receptor (anti-NMDAR) encephalitis is one of the most common paraneoplastic encephalitides. It occurs in both sexes, across all age ranges, and may occur in the presence or absence of an associated tumor. Its pathogenesis and clinical presentation relate to the presence of IgG1 or IgG3 antibodies targeting the NR1 subunit of the NMDA receptor, leading to a disinhibition of neuronal excitatory pathways. Initial clinical manifestations may be nonspecific, resembling a viral-like illness; however, with disease progression, symptoms can become quite severe, including prominent psychiatric features, cognitive problems, motor dysfunction, and autonomic instability. Anti-NMDAR encephalitis may even result in death in severe untreated cases. Diagnosis can be challenging, given that initial laboratory and radiographic results are typically nonspecific. The majority of patients respond to first or second-line treatments, although therapeutic options remain limited, usually consisting of tumor removal (if there is confirmation of an underlying malignancy) in conjunction with prompt initiation of immunosuppressive medications along with intravenous immunoglobulins and/or plasma exchange. Although the clinical presentation of anti-NMDAR encephalitis overlaps with several other more common neurological and psychiatric disorders, early diagnosis and treatment is essential for a positive prognosis. Here, we concisely review the pathogenesis, diagnosis, and clinical management of this disease.

Paraneoplastic cerebellar degeneration associated with breast cancer: A case report and review of the literature

Paraneoplastic cerebellar degeneration (PCD) is a rare neurological complication of cancer characterized by rapid development of cerebellar ataxia. We herein present a case of a 67-year-old female patient with PCD caused by breast cancer. The patient presented with progressively worsening cerebellar deficits that had been misdiagnosed for several months prior to the identification of the anti-Yo autoantibodies in the serum. A whole-body positron emission tomography/computed tomography scan revealed a lesion in the lower outer quadrant of the left breast with slightly increased metabolism. On mammography, a lobulated high-density mass was identified in the left breast. The patient underwent left breast lumpectomy and the histological examination confirmed the presence of an invasive ductal carcinoma. After breast surgery, the patient exhibited marked neurological improvement at the 12-month follow-up. Therefore, it is crucial that clinicians include paraneoplastic neurological syndromes in the differential diagnosis of neurological disorders. The detection of characterized onconeural antibodies in the serum or cerebrospinal fluid may provide guidance in the search for an underlying tumor.

Imaging Workup of Suspected Classical Paraneoplastic Neurological Syndromes: A Systematic Review and Retrospective Analysis of 18F-FDG-PET-CT

RATIONALE AND OBJECTIVES

This study aimed to assess the clinical efficacy of positron emission tomography (PET) or combined PET-computed tomography (CT) with ¹⁸F-fluorodeoxyglucose (FDG) for whole-body cancer screening in patients with suspected paraneoplastic neurological syndromes (PNS). The following main research questions were addressed: What is the percentage of positive findings to be expected in whole-body FDG-PET-CT in adult patients with PNS? How many false positives can be expected as assessed by clinical and histopathological workup? Are there patients who present with a tumor despite initially negative findings?

MATERIALS AND METHODS

This is a systematic review of the literature and retrospective analysis of FDG-PET-CT and clinical follow-up data from 45 consecutive patients (age: 56.6 ± standard deviation 15.8 years, 14 female, 31 male). Suspicious lesions were identified and correlated with immediate workup and clinical follow-up.

RESULTS

Fourteen studies were included in the review. Eleven malignancies (24.4% of patients) were identified by FDG-PET-CT in this sample. This is a higher percentage of positive findings compared to most previous reports. There was one initially negative finding.

CONCLUSIONS

Whole-body FDG-PET-CT is suitable to identify additional malignancies in patients with suspected classical PNS referred to a tertiary medical center. The utility by means of true-positive findings is higher in classical PNS than suggested by studies in less select patient populations.

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 purpose of this study was to assess the diagnostic performance of whole-body ¹⁸F-FDG PET or ¹⁸F-FDG PET/CT for detection of underlying malignancy in patients with clinically suspected neurologic and nonneurologic paraneoplastic syndromes. Methods: A systematic search was performed in PubMed (Medline), Embase, and Scopus (last updated November 2016) to identify relevant published studies reporting the performance of ¹⁸F-FDG PET or ¹⁸F-FDG PET/CT in patients with suspected paraneoplastic syndrome. Histopathologic confirmation or clinical follow-up was considered as the reference standard. Pooled estimates, with 95% confidence intervals (CIs), of sensitivity, specificity, and diagnostic odds ratio were calculated. A summary receiver-operating-characteristic curve was constructed, and the area under the curve (AUC) was determined along with the Q* index. Results: Twenty-one studies including a total of 1,293 individual patients suspected of having a paraneoplastic syndrome and who underwent ¹⁸F-FDG PET or ¹⁸F-FDG PET/CT examinations met our inclusion criteria. There was moderate to high heterogeneity among the included studies. The pooled sensitivity, specificity, and diagnostic odds ratio of ¹⁸F-FDG PET or ¹⁸F-FDG PET/CT for the detection of underlying malignancy were 0.81 (95% CI, 0.76-0.86), 0.88 (95% CI, 0.86-0.90), and 34.03 (95% CI, 18.76-61.72), respectively. The AUC and the Q* index were 0.916 (SE, 0.018) and 0.849, indicating excellent diagnostic accuracy. The diagnostic accuracy was slightly improved after studies with high applicability concerns were excluded (AUC, 0.931; SE, 0.020). In a subgroup analysis, ¹⁸F-FDG PET/CT was found to have a significantly higher specificity (0.89 vs. 0.79) than ¹⁸F-FDG PET alone, with no evidence of significant difference in the overall performance (AUC, 0.930 vs. 0.891; 2-tailed P value for difference, 0.31). Conclusion: This meta-analysis of available studies demonstrates that whole-body ¹⁸F-FDG PET or ¹⁸F-FDG PET/CT has high diagnostic accuracy and moderate to high sensitivity and specificity for detection of underlying malignancy in patients suspected of having a paraneoplastic syndrome.