[Clinical characteristics of "classical" and "non-classical" paraneoplastic neurological syndrome]

Objective: To explore the clinical features of classical and non-classical paraneoplastic neurological syndrome (PNS). Methods: From 2015 to 2020, 48 cases of definite PNS admitted to the First Affiliated Hospital of University of Science and Technology of China were retrospectively collected, and classification, clinical characteristics, onconeural antibodies and primary tumors were analyzed. The included cases were divided into classical and non-classical groups according to Graus criteria, and the differences of clinical characteristics, onconeural antibodies, combined tumors, time of diagnosis and mortality were compared between the two groups. Results: Among the 48 confirmed patients, 21 (43.8%) were positive for well-characterized onconeural antibodies. There were 28 cases (58.3%) and 20 cases (41.7%) in classic and non-classical PNS groups, respectively. No significant differences of age, sex, clinical involvement site, characteristic positive antibody type, tumor diagnosis rate and follow-up mortality were found between the two groups (all P>0.05). The time of diagnosis in the non-classical PNS group was 3.0 (2.0, 6.5) months, which was significantly longer than that in the classical PNS group 1.0(0.6, 3.0) months (P<0.05). Meanwhile, the combination rate of non-characteristic antibodies in the classical PNS group (10 cases, 35.7%) was significantly higher than that in the non-classical PNS group (1 case, 5.0%) (P=0.016). During the follow-up, 39 patients (81.3%) with tumor were confirmed, and 29 patients (60.4%) were diagnosed with PNS before the tumor was found. Conclusions: The"non-classical"PNSs are common in clinical settings. Diagnosis may be delayed due to the nonclassical symptoms of the patients. When patients have clinical symptoms related to PNS, onconeural antibodies should be detected and the relevant tumors should also be screened. Patients have positive antibodies but with no tumors should be closely followed up for more than 5 years.