Clinical features, treatment, and prognosis of nivolumab induced immune encephalitis

Immune encephalitis (IE) is an immune-mediated adverse events (irAEs) linked to nivolumab therapy, and its clinical characteristics remain unclear. This study aimed to analyze the clinical patterns of nivolumab-induced IE to inform diagnosis, treatment, and prevention strategies. We conducted a retrospective analysis of nivolumab-induced IE by reviewing case reports from the database until October 31, 2024. Among the 86 patients (53.5% male), the median age was 64 years (range 17, 83). The median time to the onset of IE was 38 days (range 4, 1430), and the median treatment cycle was 2 cycles (range 1, 18). The most prevalent symptoms included altered mental status (38.4%) and fever (37.2%). Cerebrospinal fluid analysis revealed elevated protein levels, normal glucose, and pleocytosis. Antineuronal antibodies were present in 29.1% of patients. MRI findings typically showed T2/FLAIR hyperintense signals in 52.3%. EEG results indicated diffuse slowing (16.3%). Following drug discontinuation and treatment, 86% of patients exhibited recovery or improvement, while 5.8% unfortunately succumbed to the condition. IE represents a rare yet severe irAEs associated with nivolumab. Clinicians must remain vigilant for signs of IE in patients undergoing nivolumab treatment. Diagnostic tests for nivolumab-induced IE generally do not reveal specific abnormalities. For individuals diagnosed with IE, it is crucial to initiate systemic steroid treatment without delay.