Dementia as a rare neurological adverse event of Nivolumab in a patient with metastatic renal cell carcinoma

BackgroundImmune checkpoint inhibitors (ICIs) have transformed cancer therapy but can cause immune-related adverse events (irAEs). Neurological irAEs are rare, and dementia associated with nivolumab has been rarely reported.Case PresentationA 68-year-old female with metastatic clear cell renal cell carcinoma on nivolumab since 2019 presented with progressive cognitive decline, disorientation, dysarthria, and apraxia. Brain MRI showed no metastasis, only parietal-temporal atrophy and a small meningioma. CSF analysis and paraneoplastic antibody panel were normal. Mini-Mental State Examination (MMSE) score was 14/30. Nivolumab-induced encephalitis was suspected. After 7 days of pulse methylprednisolone 1 g/day, MMSE improved to 21/30 with partial clinical recovery. The patient was started on donepezil and Ginkgo biloba extract. Current treatment is everolimus. Naranjo score was 7, indicating a probable association.ConclusionDementia is a rare but serious neurological irAE of nivolumab. Early recognition and steroid therapy may lead to partial recovery. Clinicians should be aware of cognitive dysfunction in patients on ICIs.