Polyradiculoneuropathy induced by immune checkpoint inhibitors: a case series and review of the literature

Objective: The purpose of the present study is to report the clinical characteristics of polyradiculoneuropathy induced by immune checkpoint inhibitors (ICIs). Methods: We retrospectively reviewed lists of all inpatients with neurological immune-related adverse events (irAEs) treated at the neurology departments of three hospitals in January 2017 and December 2019. We also performed a review of the previous case reports with polyradiculoneuropathy induced by ICI therapy. Results: We had 4 patients with polyradiculoneuropathy following ICI therapy. We comprehensively reviewed our 4 patients and 32 previous case reports. There were 28 men and 8 women with a mean onset age of 61 years. ICI monotherapy was performed in 27 patients, whereas the combination of ICIs was administered in 9 patients. All patients except 2 showed limb weakness, which was observed symmetrically and predominantly in the legs rather than the arms. Bulbar involvement was observed in 7 patients. The laboratory findings were demyelination in electrophysiological studies and elevated protein with lymphocytes in the cerebrospinal fluid. Disease severity was ranked on the Hughes functional scale; 17 patients were grade 4 or greater. The treatment responses to corticosteroid and intravenous methylprednisolone were favorable. Intravenous immunoglobulin was also used in combination with steroids. Seven patients died, including 4 who on mechanical ventilation. Conclusion: Polyradiculoneuropathy induced by ICIs has a distinct subset of neurological irAEs and requires early recognition.