Figure. Immune checkpoint inhibitor–induced encephalitis before and after treatment with natalizumab.

A 71-year-old woman was diagnosed in 2014 with small-cell lung cancer. In 2016, she was treated with nivolumab and ipilimumab for systemic recurrence. Four days later, she developed severe disorientation and short-term memory deficits. Brain MRI shows bilateral contrast-enhancing lesions with associated T2 hyperintensity of the hippocampi (A and B). The images normalize after 6 months of treatment with natalizumab (C and D).