Neurotoxicity as a rare side effect of immune checkpoint inhibitors. A case report and review of the literature

Neurotoxicity is a rare but often fatal immune-related adverse event (irAE). Here we report the case of a 73-year-old woman treated with pembrolizumab for metastatic bladder cancer who developed aseptic meningoencephalitis after two courses of immunotherapy. Cranial magnetic resonance imaging (cMRI) showed disseminated dot-like lesions in the terminal vascular bed of both hemispheres suggesting aseptic meningitis or vasculitis. No infectious cause could be identified in cerebrospinal fluid (CSF) cultures and polymerase chain reaction (PCR) analyses. She was treated with high-dose steroids and pre-emptive antiviral/antibiotic therapy. The patient died 6 days after onset of symptoms.