Differential diagnosis in immune checkpoint inhibitors neurotoxicity

Background: Neurologic symptoms seen in patients receiving immune checkpoint inhibitors (ICI) may not be entirely caused by immunotoxicity. We aim to highlight these confounding conditions through clinical cases to encourage early recognition and management. Methods: We describe a series of seven cases from our institution that were treated with ICI and presented with Neurologic symptoms and were diagnosed with superimposed conditions beyond immunotoxicity. Results: A total of 7 cases are described that include acute motor axonal neuropathy with vitamin B12 deficiency, lumbosacral radiculopathy with Wernicke’s, Herpes simplex virus (HSV) encephalitis reactivation, central nervous system vasculitis with renal vasculitis, myositis with fasciitis, myositis with fixed clinical deficit at resolution, and synovitis with accompanying carpal tunnel syndrome. Primary cancer site included lung adenocarcinoma (2/7), melanoma (4/7), and oropharyngeal squamous cell carcinoma (1/7). All patients had received treatment with more than one ICI. Median number of cycles prior to neurotoxicity was 3 cycles. Discussion: Neurologic symptoms seen in patients receiving ICI may include other causes beyond immunotoxicity.