Case-1: A 76-year-old man with lung adenocarcinoma presents with severe bilateral neuropathic pain and numbness in his lateral three fingers with significant loss of function after cycle 1 of anti-PD1. On the exam, he had a positive Tinel’s and Phalen’s test. Creatine kinase and LDH were normal. Electrodiagnostic studies revealed moderate-to-severe axonal sensorimotor polyneuropathy with bilateral median and ulnar nerve involvement up to the level of forearms. His findings were atypical for the commonly observed median nerve injury at the wrist. He reported gradual improvement and restoration of function with steroids and IVIG.
Case-2: A 77-year-old man with history of metastatic prostate cancer on anti-PD-1 treatment presented with bilateral severe neuropathic pain and weakness in the lower extremities for 2 weeks. Creatine kinase, myoglobin, and aldolase levels were normal. The examination revealed diffuse motor weakness, reduced sensory modalities, and absent bilateral reflexes in the lower extremities. Electrodiagnostic study showed mild-to-moderate axonal sensorimotor polyneuropathy contrary to suspected demyelinating polyradiculopathy. Lumbar puncture demonstrated hyperproteinorrachia. He was treated with steroids and plasmapheresis. He reported improvement in weakness with residual paresthesia.