113\u2005A case of suspected autoimmune encephalitis secondary to nivolumab

Abstract

Objective To describe a case of suspected immune encephalitis following nivolumab for metastatic melanoma. Methods Retrospective review of clinical records and diagnostic tests. Results A 78-year-old man with cerebral and lung melanoma metastases was treated with nivolumab, the newly developed monoclonal antibody which inhibits PD-1 deactivation of T-cells. He showed good radiological response. Three months after ceasing nivolumab, he presented to ED with acute confusion, aphasia, left-sided weakness and neglect as a stroke call. MRI demonstrated no evidence of stroke or acute encephalitis. EEG showed diffuse slowing. Lumbar puncture was not performed as he was therapeutically anticoagulated and had begun to improve on empirical antibiotics and acyclovir. One week later, he suddenly deteriorated with fevers and reduced level of consciousness. Acyclovir was restarted. Repeat EEG revealed periodic epileptic discharges over the right hemisphere and MRI demonstrated hyperintense signal and diffusion restriction of the right mesial temporal lobe suggestive of encephalitis. Subsequent lumbar puncture was negative for HSV, VZV, enterovirus, and autoimmune encephalitis antibodies. The patient’s oncology team had been in support of a course of methylprednisone on suspicion of autoimmune encephalitis, but by the time the lumbar puncture results returned he was again improving. A diagnosis of suspected nivolumab-induced encephalitis was made based on exclusion of other possible diagnoses. Conclusions The rising use of immune checkpoint inhibitors heralds an array of new and unexpected neurological complications including autoimmune encephalitis. A nationwide registry of possible cases may be helpful in improving our currently limited understanding of these emerging complications.