*Article* **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**

**Marta Opali ´nska 1, Anna Sowa-Staszczak 2,\*, Kamil W˛ezyk ˙ 3, Jeremiasz Jagiełła 4, Agnieszka Słowik <sup>4</sup> and Alicja Hubalewska-Dydejczyk <sup>2</sup>**

	- jeremiasz.jagiella@uj.edu.pl (J.J.); agnieszka.slowik@uj.edu.pl (A.S.)

**Citation:** Opali ´nska, M.;

Sowa-Staszczak, A.; W˛ezyk, K.; ˙ Jagiełła, J.; Słowik, A.; Hubalewska-Dydejczyk, A. 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. *J. Clin. Med.* **2022**, *11*, 1537. https://doi.org/10.3390/jcm11061537

Academic Editors: Arnoldo Piccardo and Francesco Fiz

Received: 7 February 2022 Accepted: 9 March 2022 Published: 11 March 2022

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**Abstract:** 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.

**Keywords:** paraneoplastic syndromes; neurooncology; [18F]FDG PET/CT; PNS
