Ramsay-Hunt syndrome and subsequent sensory neuropathy as potential immune-related adverse events of nivolumab: a case report

BACKGROUND: Nivolumab is an immune checkpoint inhibitor (ICI) and is used for the treatment of advanced non-small cell lung cancer (NSCLC). Several immune-mediated neurological adverse events associated with ICIs have been reported to date, such as Guillain-Barré syndrome. Nivolumab-associated neurological adverse events can vary, and their etiology remains unclear. CASE PRESENTATION: A 72-year-old man with NSCLC was treated with nivolumab as a second-line therapy. After 13 rounds of nivolumab therapy, he presented with Ramsay-Hunt syndrome (RHS) followed by acute ataxic sensory neuropathy. Antiviral therapy for Varicella-Zoster virus and prednisolone resulted in partial improvement of RHS, while almost no recovery was observed in the sensory neuropathy. However, the sensory ataxia significantly improved after intravenous immunoglobulin (IVIg) therapy, and interestingly, the facial palsy associated with RHS also improved. The neurological manifestations, nerve conduction study result, and imaging findings supported that dorsal root ganglia were the primary lesion site of acute ataxic sensory neuropathy. CONCLUSIONS: Our case presented with the comorbidity of RHS and subsequent ataxic sensory neuropathy after nivolumab therapy to whom IVIg was effective. Our case suggested the wide variability of possible neurological symptoms, and the potential usefulness of IVIg to sensory ataxic neuropathy, seen in cancer patients with ICI treatment.