Abstract
Paraneoplastic neurological syndrome (PNS) describes a spectrum of rare, heterogeneous neurological conditions associated with an underlying malignancy. Diagnosis of PNS is inherently difficult, with frequent misdiagnosis and delay. The literature suggests an underlying immune-mediated pathophysiology, and patients are usually tested for the presence of onconeural antibodies. With direct tumor therapy being the most effective method of stabilizing patients, there is a strong emphasis on detecting underlying tumors. The sensitivity of conventional CT imaging is often inadequate in such patients. While FDG-PET imaging has already been shown to be effective at detecting these tumors, FDG-PET/CT, combining both structural and functional imaging in a single study, is a more recent technique. To study the utility of FDG-PET/CT, we conducted a systematic literature review and a retrospective study. We identified 41 patients who underwent imaging for clinically suspected PNS at the regional PET-CT and neurosciences center based at the Royal Preston Hospital between 2007 and 2014 and compared the results to conventional investigations. Five patients had FDG-PET/CT tracer avidity suspicious of malignant disease, and four of these were subsequently diagnosed with cancer. Sensitivity and specificity were calculated to be 100 and 97.3%, respectively, with positive predictive value 80% and negative predictive value 100%. This compares to a sensitivity and specificity of 50 and 100%, respectively, for CT and 50 and 89%, respectively, for onconeural antibodies. These findings are in line with previous studies and support the diagnostic accuracy of FDG-PET/CT for the detection of underlying malignancy.
Highlights
Paraneoplastic neurological syndrome (PNS) is a rare presentation of an occult, underlying malignancy [1,2,3,4,5,6], which is often susceptible to misdiagnosis [7]
PNS is a rare and difficult diagnosis, and currently the most effective method of stabilizing the patient is direct tumor therapy. This relies on timely, accurate detection of an underlying malignancy and conventional modalities such as CT that lack the coregistration of metabolic activity provided by FDG-PET/CT imaging, are not always sufficiently sensitive [11, 23]
Patients were excluded from the study in the event that their case notes were unavailable or if the diagnosis of PNS had not been made by a consultant neurologist
Summary
Paraneoplastic neurological syndrome (PNS) is a rare presentation of an occult, underlying malignancy [1,2,3,4,5,6], which is often susceptible to misdiagnosis [7]. Such antibodies are widely regarded to prime the immune system against a mutual antigen, common to both neural tissue and underlying tumor [9], often causing irreversible neuronal damage [18] While their detection has been reported as useful to distinguish a presentation as paraneoplastic in origin [19], their use in neurological practice is inherently limited [2]. PNS is a rare and difficult diagnosis, and currently the most effective method of stabilizing the patient is direct tumor therapy This relies on timely, accurate detection of an underlying malignancy and conventional modalities such as CT that lack the coregistration of metabolic activity provided by FDG-PET/CT imaging, are not always sufficiently sensitive [11, 23]. While recent guidance does acknowledge the role of nuclear medicine in the diagnosis of selected patients [4, 5], we have evaluated the utility of this modality through a systematic review of the literature and a single center, retrospective study
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