Paraneoplastic Limbic Encephalitis in a Human Epidermal Growth Factor Receptor-2-positive Gastric Cancer Patient Treated with Trastuzumab-combined Chemotherapy: A Case Report and Literature Review.

Paraneoplastic neurological syndromes (PNSs) are rare nervous system dysfunctions in cancer patients, which are primarily observed with small-cell lung cancer, gynecological cancer, and thymoma. We herein present an uncommon case of PNS in an anti-Hu antibody-positive patient with human epidermal growth factor receptor (HER)-2-positive gastric cancer (GC), who developed limbic encephalitis and a worsening cognitive function. Trastuzumab-combined chemotherapy was initiated and appeared to be partially effective for controlling the neurological symptoms and tumor volume. Chemotherapy failure eventually led to uncontrollable neurological symptoms. This is the first case demonstrating that trastuzumab-combined chemotherapy may be effective for controlling neurological symptoms of PNS in HER2-positive GC patients.