General description

Paraneoplastic chorea (PC) is a type of paraneoplastic neurological syndrome and an important differential diagnosis for autoimmune chorea in adults. It is characterized by subacute onset, which distinguishes it from chorea caused by neurodegenerative or hereditary disorders such as Huntington's disease or senile chorea. In some cases, PC may present with atypical choreiform movements or initially lack significant imaging abnormalities, making early recognition crucial.

As with other paraneoplastic syndromes, chorea can precede the diagnosis of an underlying malignancy by months to years. The most commonly associated neoplasm is small cell lung carcinoma (SCLC), followed by thymoma, non-Hodgkin's lymphoma, and squamous cell carcinoma of the tonsil. Key antibodies involved in PC include CRMP-5 (CV2) and ANNA-1 (Hu) IgG, with CRMP-5 detected in 70% of cases associated with SCLC and 30% with thymoma.

PC often manifests alongside other neurological features, including visual disturbances, peripheral neuropathy, limbic encephalitis, or sudden loss of smell and taste, which can aid in distinguishing it from other causes of chorea. Differential diagnoses include drug-induced chorea, thyrotoxicosis, hyperglycemia, and autoimmune choreas such as Sydenham's chorea or antiphospholipid antibody syndrome, though these rarely occur in older individuals.

Radiographic features

MRI shows unilateral or asymmetric T2WI and FLAIR hyperintensity in the caudate nucleus and putamen.