Initial experience in assessing diagnostic utility of conventional and functional imaging (staging CT, PET CT, and MRI Brain/Spine) in suspected cases of paraneoplastic neurological syndrome.

Objectives: Radiology receives a large volume of referrals for systemic scans and neuroimaging in suspected cases of paraneoplastic neurological syndrome (PNS) patients. To date, there have been no guidelines to define imaging pathways in diagnosis or surveillance of such patients. This article aims to evaluate diagnostic utility of imaging in detecting positive results as well as ruling out significant pathologies in suspected cases of PNS and strategize vetting requests. Materials and Methods: Retrospectively evaluated scan records, onconeuronal antibody results of 80 patients (separated into below and over 60s age group) referred with suspected PNS (categorized as classical or probable PNS after neurological assessment). Imaging findings and final diagnoses were classified into three groups: Normal (N), non-neoplastic significant findings (S), and malignancies (M) after evaluating histopathology results/ perioperative findings and treatment notes. Results: There were ten cases of biopsy-proven malignancies and 18 cases of non-neoplastic significant conditions (predominantly neurological) with malignancies dominating in the elderly age group, demyelinating neurological conditions in below 60s group and patients suspected of classical PNS on neurological evaluation. Staging computed tomography (CT) had 50%, positron emission tomography CT (PETCT) had 80%, sensitivity had 93%, and negative predictive value in ruling out malignancy had 96%. Magnetic resonance of brain and spine was reported abnormal in 68% of finally diagnosed positive cases while only 11% cases demonstrated onconeuronal antibody positivity. Conclusion: Complete neuroimaging before systemic scans, categorization of referral requests in probable and classical cases of PNS with prioritization of PET in cases of high clinical concern might help in better detection of pathologies and reduce unnecessary CTs.