To report a rare, debilitating neurotoxicity to combination immunotherapy. 

Neurologic immune related adverse events associated with ICI are rare; rapid diagnosis and treatment can limit morbidity. Combined ICI treatment is associated with more severe and rapid neurotoxicity. Only 4 BPN cases have been reported. Three were unilateral, predominantly involving the lower trunk (C8-T1) and highly steroid responsive. One affected the anterior interosseous and lateral antebrachial cutaneous nerves.

A 76-year-old woman with lung adenocarcinoma received 3 doses of Nivolumab and one dose of Ipilimumab. She developed numbness and pain, followed by worsening bilateral asymmetric arm weakness 3 weeks after receiving her last Nivolumab dose. Her weakness was diffuse, worse on the right, associated with loss of reflexes. It started on the right arm and involved left arm a week after.

This may be the first report of bilateral sequential BPN with predominantly upper-mid trunk involvement after dual treatment with Nivolumab and Ipilimumab. Rapid workup, exclusion of confounding factors, and treatment with steroids and immunomodulating agents can lead to significant recovery of function from a debilitating process.