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.