18F-FDG PET/CT in the evaluation of patients suspected of paraneoplastic neurological syndrome

Abstract Objective This study aimed to determine the diagnostic impact of 18 F-FDG PET/CT based on the clinical features of paraneoplastic neurological syndrome (PNS). Material and methods Multicenter retrospective and longitudinal study of patients with suspicion of PNS. The clinical picture was classified into classic (CS) and non-classic syndrome (NCS). After the follow-up, the definitive or possible diagnosis of PNS was established. The pictures that did not match any of the previous criteria were categorised as non-classifiable. The state of the onconeural antibodies was studied. The PET/CT was classified as positive or negative for the detection of malignancy. The relationship between PET/CT findings and the final diagnosis was determined. The differences between variables (Pearson test X 2 ) and the relationship between the results of the PET/CT and the final diagnosis was analysed. Results A total of 64 patients were analysed, classifying 30% as CS and 42% as NCS. After the follow-up, 20% and 16% of subjects were diagnosed as possible and definitive PNS, respectively. Positive onconeural antibodies were found in 13% of the patients. A definitive diagnosis of PNS was associated with a positive PET/CT ( p  = .08). A significant relation between antibodies expression and final diagnosis of neoplasia ( p  = .04) was demonstrated. The PET/CT correctly localised malignancy in 5/7 cases of invasive cancer. Conclusions The PET/CT showed a higher percentage of positive results in patients with definitive diagnosis of PNS. Despite the low prevalence of malignancy in our series, the PET/CT detected malignancy in a significant proportion of patients with invasive cancer.