Immune-related meningoencephalitis: case reportA 68-year-old man developed immune-related meningoencephalitis during treatment with nivolumab for stage IVA adenocarcinoma of the lung (cT4N0M1b).The man with medical history of anxiety and depression treated with clonazepam and venlafaxine. In February 2018, he presented with chest pain. Based on multiple examinations, he was diagnosed with stage IVA adenocarcinoma of the lung (cT4N0M1b). Thus, he started receiving chemotherapy with cisplatin and pemetrexed. He received four cycles of chemotherapy from March to May 2018. After 4 cycles of chemotherapy, the CT-Scan showed progressive disease with enlargement of the adrenal M1. Therefore, in June 2018, he was started on nivolumab 3 mg/kg every two weeks [total dose of 240mg according to weight of 80kg; route not stated]. He received a total 46 cycles of nivolumab therapy with partial response. After the first 2 months of nivolumab therapy, he presented grade I arthralgias and low fever. In April 2020 amid the SARS-COV-2 pandemic, nivolumab higher flat-dosing was proposed. He received two cycles of nivolumab 480mg every 4 weeks. After 24 hours of the first higher flat-dose administration, he presented low fever, somnolence, slowed mental response, hand tremor and asthenia with a spontaneous complete remission in 10 days. After 10 days of the second higher flat-dose administration, he was shifted to the emergency room (ER) after 12 hour of fever syndrome, headache, altered mental status with visual hallucinations, language impairment, psychomotor agitation and gait instability. He was admitted to hospital. On admission, his concomitant medications included clonazepam, venlafaxine and a transdermal fentanyl patch. At the ER, he presented temporo-spatial disorientation with mixed aphasia. Subsequently, the lumbar puncture showed an inflammatory CSF with 7 cell/mm 3 (all of them lymphocytes) and 0.76 g/L of protein.Consequently, the man was empirically treated with methylprednisolone and aciclovir. A brain MRI did not show enhancements suggesting brain metastases or leptomeningeal involvement. Based on these examinations, a diagnosis of immune-related meningoencephalitis was made. Aciclovir was stopped. During the hospital stay, he presented a favourable outcome. At discharge, he had mild slowed mental response and disorientation with no language impairment, and he was able to walk without assistance. After 15 days of discharge from hospital, his repeat lumbar puncture showed an inflammatory CSF with 4 cell/mm 3 , normal levels of glucose and protein. In the following weeks, he experienced a progressive cognitive recovery. At discharge, he was on tapering methylprednisolone therapy.In July 2020, the man was re-started on nivolumab 3 mg/kg every 2 weeks therapy. Meanwhile, he was continued on tapering methylprednisolone. Without concerning symptoms recurrence, methylprednisolone therapy was completed in October 2020. He received 7 cycles of nivolumab while tapering methylprednisolone therapy (from July to October 2020) and...