Nivolumab-induced seronegative encephalitis

Immune checkpoint inhibitors (ICIs) have emerged as a new therapeutic tool for numerous types of cancer. Neurological complications have been reported in 1% of patients who have undergone checkpoint inhibition therapy. ICIs-induced encephalitides occur in 0.1-0.2% of patients within weeks after ICIs initiation; are usually seronegative and have nonspecific changes on imaging, CSF and electroencephalogram (EEG) studies. Early recognition and prompt treatment are important to prevent significant morbidity and mortality. We present a case of nivolumab-induced encephalitis with very subtle clinical symptoms and full recovery following ICIs suspension and steroids.