Rare Co-Occurrence: Paraneoplastic Striatal Encephalitis with a Metastatic Lesion in Small Cell Lung Cancer.

We present a rare case of striatal encephalitis associated with small cell lung cancer (SCLC), manifesting as a choreiform movement disorder. A 57-year-old woman presented with a subacute onset of involuntary movements. Despite extensive investigations, the etiology of this choreiform movement disorder remained elusive until a detailed evaluation of clinical signs and radiological findings revealed SCLC. In addition, she had an asymptomatic metastatic brain parenchymal lesion. This case highlights the importance of considering paraneoplastic striatal encephalitis (PSE), a rare presenting neurological syndrome.