The current state of the paraneoplastic neurological syndromes problem

Abstract

Paraneoplastic syndromes (PS) are immune-mediated manifestations of a distant oncological process, which is a reaction of autoantibodies against antigens expressed by the tumor. These syndromes are divided into neurological, endocrine, hematological, and dermatological. PS can be diagnosed before or in parallel with tumor detection and often masquerade as neurological or psychiatric disorders. The review discusses the updated 2021 diagnostic criteria, which include revisions to diagnostic levels since 2004, as well as new classifications of antibodies based on the pathogenetic mechanisms of nerve cell damage and their frequency of detection in patients. The phenotypes of high-, medium-, and low-risk paraneoplastic neurological syndromes (PNS) are highlighted, with a special emphasis on the clinical features of high-risk phenotypes. Particular attention is paid to limbic encephalitis, its clinical signs, specific antibodies, instrumental and laboratory studies, and associated oncological diseases. Encephalomyelitis and subacute cerebellar degeneration are also discussed, detailing pathological changes, key antibodies and neoplasia, emphasizing the need for differential diagnosis and immunosuppressive treatment. General features about opsoclonus myoclonus syndrome, its clinical manifestations and causes, as well as Lambert—Eaton myasthenic syndrome are provided, in particular, its association with small cell lung cancer is emphasized, and the features of diagnosis, differential diagnosis with myasthenia gravis and treatment are highlighted. Based on the updated diagnostic criteria, the data analysis will provide clinicians with guidelines for identifying specific phenotypes of PNS and associated antibodies, which are key to improving diagnostic processes and selecting an effective treatment strategy.