Paraneoplastic neurological syndromes in the era of immune-checkpoint inhibitors

Paraneoplastic neurological syndromes (PNSs) comprise a group of disorders that can affect any part of the nervous system in patients with cancer and frequently result from autoimmune responses triggered by the ectopic expression of neuronal proteins in cancer cells. These disorders are rare, although the introduction of immune-checkpoint inhibitors (ICIs) into cancer treatment algorithms has renewed interest in PNSs. ICIs are associated with a considerably increased incidence of immunological toxicities compared with traditional anticancer therapies, including neurological immune-related adverse effects (nirAEs) that can manifest as PNSs. Theoretically, the use of ICIs might increase the risk of PNSs, in particular, in patients with the types of cancer that are most frequently associated with these disorders (such as small-cell lung cancer), emphasizing the importance of their prompt diagnosis and treatment to prevent irreversible neurological deficits. To facilitate the recognition of these disorders in the context of immune-checkpoint inhibition, we provide an overview of PNSs, including the main syndromes, types of neuronal autoantibodies and associated immunological mechanisms. We also review the scenarios in which nirAEs fulfil the criteria for PNSs and examine their frequency and clinical presentations. Finally, we provide recommendations for the prevention and management of PNSs that can occur during ICI therapy.